Keep the image-adjustment panel out of the lines its neighbours change

The branch collided with the Image gizmo branch in four places that are not
real disagreements, only two features reaching for the same line:

- the layer's preview_adjust field and the three new declarations in
  TextureDisplacement.hpp sat at the same two insertion points
- the panel's member block sat on top of m_erase_mode, which the other
  branch moves to protected
- all three texture getters grew an adjustment clause in the same if, and
  one of those ifs is rewritten there too

The first three are moved a few lines away. The cache keys are dropped: the
panel now calls invalidate_adjust_textures() when it moves or reverts the
adjustment, which is less code than three widened keys and leaves the
getters alone. 'cog.svg' and the panel's tests also move to a line of their
own, for the same reason.

resources/shaders/110/texture_displacement_shaded.fs

@@ -72,21 +72,17 @@ varying float weight;
 varying float island_active;
 varying vec2  vertex_uv;
 
-// The cylinder's own frame, built exactly as libslic3r's project_cylindrical() builds it - right
-// handed, so the angle taken from it grows anticlockwise about the axis, which seen from outside the
-// cylinder is to the viewer's right rather than mirrored.
+// The cylinder's own frame, built exactly as libslic3r's project_cylindrical() builds it - including
+// the handedness, which comes out left-handed for an axis of +Z. Copied rather than "corrected", so
+// the preview wraps the texture the same way round as the bake.
 void cylinder_frame(out vec3 up, out vec3 right, out vec3 fwd)
 {
     up = (length(patch_axis) > 1e-8) ? normalize(patch_axis) : vec3(0.0, 0.0, 1.0);
     vec3 arbitrary = (abs(up.z) < 0.9) ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
     right = normalize(cross(up, arbitrary));
-    fwd   = normalize(cross(up, right));
+    fwd   = normalize(cross(right, up));
 }
 
-// Which side of a world plane a face is on, with zero counting as the positive side. Not GLSL's own
-// sign(), which returns 0 there and would collapse the coordinate onto a line.
-float box_face_sign(float n) { return n >= 0.0 ? 1.0 : -1.0; }
-
 // The raw, millimetre-valued projection of `p` (a position in the texture frame), before the layer's
 // tiling/rotation/aspect/offset - a term-for-term transcription of libslic3r's project_planar(),
 // project_cylindrical() and project_spherical(). `n` is read by the planar mode only.
@@ -98,7 +94,7 @@ vec2 projection_raw(vec3 p, vec3 n)
         vec3  rel = p - patch_center;
         float x   = dot(rel, right);
         float y   = dot(rel, fwd);
-        return vec2(atan(y, x) * sqrt(x * x + y * y), -dot(rel, up));
+        return vec2(atan(y, x) * sqrt(x * x + y * y), dot(rel, up));
     }
     if (projection_mode == 2) {                 // Spherical: (longitude, latitude) * radius
         vec3  rel    = p - patch_center;
@@ -106,18 +102,10 @@ vec2 projection_raw(vec3 p, vec3 n)
         if (radius < 1e-8)
             return vec2(0.0);
         vec3 dir = rel / radius;
-        return vec2(atan(dir.y, dir.x), -asin(clamp(dir.z, -1.0, 1.0))) * radius;
+        return vec2(atan(dir.y, dir.x), asin(clamp(dir.z, -1.0, 1.0))) * radius;
     }
-    // Triplanar: drop the dominant normal axis. v is negated so the image's first pixel row (v = 0)
-    // sits at the top of the model instead of upside down, and u is flipped on the far side of each
-    // plane so the two faces sharing it are not mirror images. libslic3r's box_plane_yz() and its two
-    // siblings, term for term.
-    vec3 an = abs(n);
-    if (an.x >= an.y && an.x >= an.z)
-        return vec2(box_face_sign(n.x) * p.y, -p.z);
-    if (an.y >= an.x && an.y >= an.z)
-        return vec2(-box_face_sign(n.y) * p.x, -p.z);
-    return vec2(box_face_sign(n.z) * p.x, -p.y);
+    vec3 an = abs(n);                           // Triplanar: drop the dominant normal axis
+    return (an.x >= an.y && an.x >= an.z) ? p.yz : ((an.y >= an.x && an.y >= an.z) ? p.xz : p.xy);
 }
 
 // The two surface directions projection_raw()'s u and v run along at `p`, plus how many raw units one
@@ -136,7 +124,7 @@ void projection_axes(vec3 p, vec3 n, out vec3 t, out vec3 b, out vec2 units_per_
         vec2  xy  = vec2(dot(rel, right), dot(rel, fwd));
         float r   = length(xy);
         t = (r > 1e-6) ? (fwd * xy.x - right * xy.y) / r : right; // circumferential: u runs along it
-        b = -up;                                                  // v is the distance *against* the axis
+        b = up;                                                   // v is the distance along the axis
         return;
     }
     if (projection_mode == 2) {
@@ -145,20 +133,20 @@ void projection_axes(vec3 p, vec3 n, out vec3 t, out vec3 b, out vec2 units_per_
         vec3  dir = (r > 1e-8) ? rel / r : vec3(0.0, 0.0, 1.0);
         float c   = length(dir.xy);                               // cos(latitude)
         t = (c > 1e-6) ? vec3(-dir.y, dir.x, 0.0) / c : vec3(1.0, 0.0, 0.0);
-        b = -cross(dir, t);                                       // v grows away from the pole, unit length
+        b = cross(dir, t);                                        // increasing latitude, unit length
         units_per_mm = vec2(1.0 / max(c, 1e-3), 1.0);
         return;
     }
-    vec3 an = abs(n);                          // the same signed basis projection_raw() uses
-    if (an.x >= an.y && an.x >= an.z) {        // planar = (+-y, -z)
-        t = vec3(0.0, box_face_sign(n.x), 0.0);
-        b = vec3(0.0, 0.0, -1.0);
-    } else if (an.y >= an.x && an.y >= an.z) { // planar = (+-x, -z)
-        t = vec3(-box_face_sign(n.y), 0.0, 0.0);
-        b = vec3(0.0, 0.0, -1.0);
-    } else {                                   // planar = (+-x, -y)
-        t = vec3(box_face_sign(n.z), 0.0, 0.0);
-        b = vec3(0.0, -1.0, 0.0);
+    vec3 an = abs(n);
+    if (an.x >= an.y && an.x >= an.z) {        // planar = p.yz
+        t = vec3(0.0, 1.0, 0.0);
+        b = vec3(0.0, 0.0, 1.0);
+    } else if (an.y >= an.x && an.y >= an.z) { // planar = p.xz
+        t = vec3(1.0, 0.0, 0.0);
+        b = vec3(0.0, 0.0, 1.0);
+    } else {                                   // planar = p.xy
+        t = vec3(1.0, 0.0, 0.0);
+        b = vec3(0.0, 1.0, 0.0);
     }
 }
 

resources/shaders/110/texture_displacement_uvcheck.fs

@@ -36,20 +36,14 @@ varying vec4  world_pos;
 varying float distortion;
 varying vec2  vertex_uv;
 
-// Right handed (up x right), like libslic3r's project_cylindrical(), so the angle taken from it grows
-// anticlockwise about the axis - to the viewer's right when seen from outside the cylinder.
 void cylinder_frame(out vec3 up, out vec3 right, out vec3 fwd)
 {
     up = (length(patch_axis) > 1e-8) ? normalize(patch_axis) : vec3(0.0, 0.0, 1.0);
     vec3 arbitrary = (abs(up.z) < 0.9) ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
     right = normalize(cross(up, arbitrary));
-    fwd   = normalize(cross(up, right));
+    fwd   = normalize(cross(right, up));
 }
 
-// Which side of a world plane a face is on, with zero counting as the positive side. Not GLSL's own
-// sign(), which returns 0 there and would collapse the coordinate onto a line.
-float box_face_sign(float n) { return n >= 0.0 ? 1.0 : -1.0; }
-
 // Term for term libslic3r's project_planar() / project_cylindrical() / project_spherical(), in mm.
 vec2 projection_raw(vec3 p, vec3 n)
 {
@@ -59,7 +53,7 @@ vec2 projection_raw(vec3 p, vec3 n)
         vec3  rel = p - patch_center;
         float x   = dot(rel, right);
         float y   = dot(rel, fwd);
-        return vec2(atan(y, x) * sqrt(x * x + y * y), -dot(rel, up));
+        return vec2(atan(y, x) * sqrt(x * x + y * y), dot(rel, up));
     }
     if (projection_mode == 2) {
         vec3  rel    = p - patch_center;
@@ -67,16 +61,10 @@ vec2 projection_raw(vec3 p, vec3 n)
         if (radius < 1e-8)
             return vec2(0.0);
         vec3 dir = rel / radius;
-        return vec2(atan(dir.y, dir.x), -asin(clamp(dir.z, -1.0, 1.0))) * radius;
+        return vec2(atan(dir.y, dir.x), asin(clamp(dir.z, -1.0, 1.0))) * radius;
     }
-    // v negated so the image's first pixel row sits at the top of the model, u flipped on the far side
-    // of each plane so the two faces sharing it are not mirror images - see libslic3r's box_plane_yz().
     vec3 an = abs(n);
-    if (an.x >= an.y && an.x >= an.z)
-        return vec2(box_face_sign(n.x) * p.y, -p.z);
-    if (an.y >= an.x && an.y >= an.z)
-        return vec2(-box_face_sign(n.y) * p.x, -p.z);
-    return vec2(box_face_sign(n.z) * p.x, -p.y);
+    return (an.x >= an.y && an.x >= an.z) ? p.yz : ((an.y >= an.x && an.y >= an.z) ? p.xz : p.xy);
 }
 
 vec2 project_uv(vec3 p, vec3 n)

resources/shaders/140/texture_displacement_shaded.fs

@@ -138,21 +138,17 @@ in vec2  vertex_uv;
 
 out vec4 out_color;
 
-// The cylinder's own frame, built exactly as libslic3r's project_cylindrical() builds it - right
-// handed, so the angle taken from it grows anticlockwise about the axis, which seen from outside the
-// cylinder is to the viewer's right rather than mirrored.
+// The cylinder's own frame, built exactly as libslic3r's project_cylindrical() builds it - including
+// the handedness, which comes out left-handed for an axis of +Z. Copied rather than "corrected", so
+// the preview wraps the texture the same way round as the bake.
 void cylinder_frame(out vec3 up, out vec3 right, out vec3 fwd)
 {
     up = (length(patch_axis) > 1e-8) ? normalize(patch_axis) : vec3(0.0, 0.0, 1.0);
     vec3 arbitrary = (abs(up.z) < 0.9) ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
     right = normalize(cross(up, arbitrary));
-    fwd   = normalize(cross(up, right));
+    fwd   = normalize(cross(right, up));
 }
 
-// Which side of a world plane a face is on, with zero counting as the positive side. Not GLSL's own
-// sign(), which returns 0 there and would collapse the coordinate onto a line.
-float box_face_sign(float n) { return n >= 0.0 ? 1.0 : -1.0; }
-
 // The raw, millimetre-valued projection of `p` (a position in the texture frame), before the layer's
 // tiling/rotation/aspect/offset - a term-for-term transcription of libslic3r's project_planar(),
 // project_cylindrical() and project_spherical(). `n` is read by the planar mode only.
@@ -164,7 +160,7 @@ vec2 projection_raw(vec3 p, vec3 n)
         vec3  rel = p - patch_center;
         float x   = dot(rel, right);
         float y   = dot(rel, fwd);
-        return vec2(atan(y, x) * sqrt(x * x + y * y), -dot(rel, up));
+        return vec2(atan(y, x) * sqrt(x * x + y * y), dot(rel, up));
     }
     if (projection_mode == 2) {                 // Spherical: (longitude, latitude) * radius
         vec3  rel    = p - patch_center;
@@ -172,18 +168,10 @@ vec2 projection_raw(vec3 p, vec3 n)
         if (radius < 1e-8)
             return vec2(0.0);
         vec3 dir = rel / radius;
-        return vec2(atan(dir.y, dir.x), -asin(clamp(dir.z, -1.0, 1.0))) * radius;
+        return vec2(atan(dir.y, dir.x), asin(clamp(dir.z, -1.0, 1.0))) * radius;
     }
-    // Triplanar: drop the dominant normal axis. v is negated so the image's first pixel row (v = 0)
-    // sits at the top of the model instead of upside down, and u is flipped on the far side of each
-    // plane so the two faces sharing it are not mirror images. libslic3r's box_plane_yz() and its two
-    // siblings, term for term.
-    vec3 an = abs(n);
-    if (an.x >= an.y && an.x >= an.z)
-        return vec2(box_face_sign(n.x) * p.y, -p.z);
-    if (an.y >= an.x && an.y >= an.z)
-        return vec2(-box_face_sign(n.y) * p.x, -p.z);
-    return vec2(box_face_sign(n.z) * p.x, -p.y);
+    vec3 an = abs(n);                           // Triplanar: drop the dominant normal axis
+    return (an.x >= an.y && an.x >= an.z) ? p.yz : ((an.y >= an.x && an.y >= an.z) ? p.xz : p.xy);
 }
 
 // The two surface directions projection_raw()'s u and v run along at `p`, plus how many raw units one
@@ -202,7 +190,7 @@ void projection_axes(vec3 p, vec3 n, out vec3 t, out vec3 b, out vec2 units_per_
         vec2  xy  = vec2(dot(rel, right), dot(rel, fwd));
         float r   = length(xy);
         t = (r > 1e-6) ? (fwd * xy.x - right * xy.y) / r : right; // circumferential: u runs along it
-        b = -up;                                                  // v is the distance *against* the axis
+        b = up;                                                   // v is the distance along the axis
         return;
     }
     if (projection_mode == 2) {
@@ -211,20 +199,20 @@ void projection_axes(vec3 p, vec3 n, out vec3 t, out vec3 b, out vec2 units_per_
         vec3  dir = (r > 1e-8) ? rel / r : vec3(0.0, 0.0, 1.0);
         float c   = length(dir.xy);                               // cos(latitude)
         t = (c > 1e-6) ? vec3(-dir.y, dir.x, 0.0) / c : vec3(1.0, 0.0, 0.0);
-        b = -cross(dir, t);                                       // v grows away from the pole, unit length
+        b = cross(dir, t);                                        // increasing latitude, unit length
         units_per_mm = vec2(1.0 / max(c, 1e-3), 1.0);
         return;
     }
-    vec3 an = abs(n);                          // the same signed basis projection_raw() uses
-    if (an.x >= an.y && an.x >= an.z) {        // planar = (+-y, -z)
-        t = vec3(0.0, box_face_sign(n.x), 0.0);
-        b = vec3(0.0, 0.0, -1.0);
-    } else if (an.y >= an.x && an.y >= an.z) { // planar = (+-x, -z)
-        t = vec3(-box_face_sign(n.y), 0.0, 0.0);
-        b = vec3(0.0, 0.0, -1.0);
-    } else {                                   // planar = (+-x, -y)
-        t = vec3(box_face_sign(n.z), 0.0, 0.0);
-        b = vec3(0.0, -1.0, 0.0);
+    vec3 an = abs(n);
+    if (an.x >= an.y && an.x >= an.z) {        // planar = p.yz
+        t = vec3(0.0, 1.0, 0.0);
+        b = vec3(0.0, 0.0, 1.0);
+    } else if (an.y >= an.x && an.y >= an.z) { // planar = p.xz
+        t = vec3(1.0, 0.0, 0.0);
+        b = vec3(0.0, 0.0, 1.0);
+    } else {                                   // planar = p.xy
+        t = vec3(1.0, 0.0, 0.0);
+        b = vec3(0.0, 1.0, 0.0);
     }
 }
 

resources/shaders/140/texture_displacement_uvcheck.fs

@@ -47,20 +47,14 @@ in vec2  vertex_uv;
 
 out vec4 out_color;
 
-// Right handed (up x right), like libslic3r's project_cylindrical(), so the angle taken from it grows
-// anticlockwise about the axis - to the viewer's right when seen from outside the cylinder.
 void cylinder_frame(out vec3 up, out vec3 right, out vec3 fwd)
 {
     up = (length(patch_axis) > 1e-8) ? normalize(patch_axis) : vec3(0.0, 0.0, 1.0);
     vec3 arbitrary = (abs(up.z) < 0.9) ? vec3(0.0, 0.0, 1.0) : vec3(1.0, 0.0, 0.0);
     right = normalize(cross(up, arbitrary));
-    fwd   = normalize(cross(up, right));
+    fwd   = normalize(cross(right, up));
 }
 
-// Which side of a world plane a face is on, with zero counting as the positive side. Not GLSL's own
-// sign(), which returns 0 there and would collapse the coordinate onto a line.
-float box_face_sign(float n) { return n >= 0.0 ? 1.0 : -1.0; }
-
 // Term for term libslic3r's project_planar() / project_cylindrical() / project_spherical(), in mm.
 vec2 projection_raw(vec3 p, vec3 n)
 {
@@ -70,7 +64,7 @@ vec2 projection_raw(vec3 p, vec3 n)
         vec3  rel = p - patch_center;
         float x   = dot(rel, right);
         float y   = dot(rel, fwd);
-        return vec2(atan(y, x) * sqrt(x * x + y * y), -dot(rel, up));
+        return vec2(atan(y, x) * sqrt(x * x + y * y), dot(rel, up));
     }
     if (projection_mode == 2) {
         vec3  rel    = p - patch_center;
@@ -78,16 +72,10 @@ vec2 projection_raw(vec3 p, vec3 n)
         if (radius < 1e-8)
             return vec2(0.0);
         vec3 dir = rel / radius;
-        return vec2(atan(dir.y, dir.x), -asin(clamp(dir.z, -1.0, 1.0))) * radius;
+        return vec2(atan(dir.y, dir.x), asin(clamp(dir.z, -1.0, 1.0))) * radius;
     }
-    // v negated so the image's first pixel row sits at the top of the model, u flipped on the far side
-    // of each plane so the two faces sharing it are not mirror images - see libslic3r's box_plane_yz().
     vec3 an = abs(n);
-    if (an.x >= an.y && an.x >= an.z)
-        return vec2(box_face_sign(n.x) * p.y, -p.z);
-    if (an.y >= an.x && an.y >= an.z)
-        return vec2(-box_face_sign(n.y) * p.x, -p.z);
-    return vec2(box_face_sign(n.z) * p.x, -p.y);
+    return (an.x >= an.y && an.x >= an.z) ? p.yz : ((an.y >= an.x && an.y >= an.z) ? p.xz : p.xy);
 }
 
 vec2 project_uv(vec3 p, vec3 n)

src/libslic3r/TextureDisplacement.cpp

@@ -157,12 +157,33 @@ struct SmoothedTextureCache
     {
         std::weak_ptr<const std::vector<unsigned char>> source;
         float                                           smoothing = 0.f;
+        // Part of the key, not of the result: smoothing is applied *after* the panel's adjustments, so a
+        // blur computed over one set of adjustments is not the blur another set would give.
+        TextureAdjustments                              adjust;
         DecodedHeightTexture                            texture;
     };
     std::mutex                                   mutex;
     std::unordered_map<const void *, Entry>      entries;
 };
 SmoothedTextureCache g_smoothed_texture_cache;
+
+// The adjusted copy, cached between the raw decode and the smoothed one. Needed for the same reason the
+// smoothed cache is: while a slider in the image-adjustment panel moves, the thumbnail, the shaded
+// preview's height and colour textures, the UV editor backdrop and the displacement preview job all ask
+// for the same (image, adjustments) pair within one frame, and each of them running a full-size resample
+// of its own is what would make the panel unusable on a large texture.
+struct AdjustedTextureCache
+{
+    struct Entry
+    {
+        std::weak_ptr<const std::vector<unsigned char>> source;
+        TextureAdjustments                              adjust;
+        DecodedHeightTexture                            texture;
+    };
+    std::mutex                              mutex;
+    std::unordered_map<const void *, Entry> entries;
+};
+AdjustedTextureCache g_adjusted_texture_cache;
 } // namespace
 
 namespace {
@@ -338,6 +359,34 @@ DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer
         entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data), result };
     }
 
+    // The image-adjustment panel's live edits, on top of the decode and before the smoothing. Before,
+    // because `preview_adjust` is an edit to the image while `smoothing` is a live low-pass over whatever
+    // the image is - the same order the panel presents them in, and the same order a commit bakes in.
+    //
+    // Nothing applies here once the panel has closed: it resets preview_adjust to identity, and identity
+    // is a no-op that costs one comparison.
+    if (!layer.preview_adjust.identity()) {
+        bool have_adjusted = false;
+        {
+            std::lock_guard<std::mutex> lock(g_adjusted_texture_cache.mutex);
+            auto it = g_adjusted_texture_cache.entries.find(key);
+            if (it != g_adjusted_texture_cache.entries.end() && it->second.adjust == layer.preview_adjust &&
+                it->second.source.lock() == layer.image_data) {
+                result        = it->second.texture;
+                have_adjusted = true;
+            }
+        }
+        if (!have_adjusted) {
+            result = apply_texture_adjustments(result, layer.preview_adjust);
+            std::lock_guard<std::mutex> lock(g_adjusted_texture_cache.mutex);
+            auto &entries = g_adjusted_texture_cache.entries;
+            for (auto it = entries.begin(); it != entries.end();)
+                it = it->second.source.expired() ? entries.erase(it) : std::next(it);
+            entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data),
+                             layer.preview_adjust, result };
+        }
+    }
+
     // Smoothing radius scales with the texture so the same slider value blurs the same *fraction* of
     // the image whatever resolution it came in at, and stays continuous in the slider - see
     // smooth_height_pixels(). The cap is a cost limit, not part of the mapping: the blur is
@@ -348,7 +397,7 @@ DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer
             std::lock_guard<std::mutex> lock(g_smoothed_texture_cache.mutex);
             auto it = g_smoothed_texture_cache.entries.find(key);
             if (it != g_smoothed_texture_cache.entries.end() && it->second.smoothing == layer.smoothing &&
-                it->second.source.lock() == layer.image_data)
+                it->second.adjust == layer.preview_adjust && it->second.source.lock() == layer.image_data)
                 return it->second.texture;
         }
         const float span   = 0.05f * float(std::min(result.width, result.height));
@@ -372,12 +421,70 @@ DecodedHeightTexture decode_height_texture(const TextureDisplacementLayer &layer
         auto &entries = g_smoothed_texture_cache.entries;
         for (auto it = entries.begin(); it != entries.end();)
             it = it->second.source.expired() ? entries.erase(it) : std::next(it);
-        entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data), layer.smoothing, result };
+        entries[key] = { std::weak_ptr<const std::vector<unsigned char>>(layer.image_data), layer.smoothing,
+                         layer.preview_adjust, result };
     }
     return result;
 }
 
 namespace {
+// Fraction of the short side that TextureAdjustments::blur == 1 blurs over, and the cost cap on it.
+// Deliberately the same pair decode_height_texture() uses for the Smoothing slider - see
+// adjustment_blur_radius().
+constexpr float SOURCE_BLUR_SPAN   = 0.05f;
+constexpr float SOURCE_BLUR_MAX_PX = 48.f;
+
+// Radius of the unsharp mask's blurred reference, in texels. Small and only mildly resolution-dependent:
+// a sharpen is meant to act on the finest detail the image holds, so its radius tracks the texel grid
+// rather than the picture's size. 1024x1024 gives ~2 texels, the usual photo-editor default.
+float unsharp_radius(int width, int height)
+{
+    return std::max(1.f, 0.002f * float(std::min(width, height)));
+}
+
+// Brightness as a *lift* toward white (or toward black) rather than an additive offset: positive b maps
+// v to v + b*(1 - v), negative to v*(1 + b). Both reach the endpoint exactly at |b| == 1 while staying
+// monotonic and non-clipping in between, which an additive shift does not - it drives a whole region to
+// a flat 255 and, because this image is also the height map, that region bakes as flat relief rather
+// than as bright relief. Keeping the curve injective keeps the detail in it.
+float apply_brightness(float v, float b)
+{
+    return b >= 0.f ? v + b * (1.f - v) : v * (1.f + b);
+}
+
+// Contrast about the 0.5 pivot. Gain is 1/(1-c) going up (c == 1 would be an infinite-slope threshold, so
+// the caller's clamp keeps it finite) and 1+c going down, reaching a flat mid-grey at c == -1.
+float apply_contrast(float v, float c)
+{
+    const float gain = c >= 0.f ? 1.f / std::max(1e-3f, 1.f - c) : 1.f + c;
+    return (v - 0.5f) * gain + 0.5f;
+}
+
+// Blur then sharpen one 8-bit channel in place. Shared by the grayscale path and by each of a colour
+// image's three channels, so every channel gets the identical spatial treatment and a colour image's
+// hue cannot shift just because its channels were filtered differently.
+void adjust_channel_spatial(std::vector<uint8_t> &channel, int width, int height, float blur, float sharpness)
+{
+    if (blur > 0.f)
+        smooth_height_pixels(channel, width, height, adjustment_blur_radius(blur, width, height));
+
+    if (sharpness <= 0.f)
+        return;
+
+    // Unsharp mask: push each texel away from its local average by `amount` times the difference. The
+    // blurred reference is a copy, so the sharpen reads the un-sharpened neighbourhood everywhere rather
+    // than its own partly-written output.
+    std::vector<uint8_t> base = channel;
+    smooth_height_pixels(base, width, height, unsharp_radius(width, height));
+    const float amount = 1.5f * std::clamp(sharpness, 0.f, 1.f);
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, channel.size()), [&](const tbb::blocked_range<size_t> &r) {
+        for (size_t i = r.begin(); i < r.end(); ++i) {
+            const float v = float(channel[i]) + amount * (float(channel[i]) - float(base[i]));
+            channel[i]    = uint8_t(std::lround(std::clamp(v, 0.f, 255.f)));
+        }
+    });
+}
+
 struct TextureDetailCache
 {
     std::mutex mutex;
@@ -386,6 +493,150 @@ struct TextureDetailCache
 TextureDetailCache g_texture_detail_cache;
 } // namespace
 
+float adjustment_blur_radius(float blur, int width, int height)
+{
+    if (blur <= 0.f || width <= 0 || height <= 0)
+        return 0.f;
+    const float span = SOURCE_BLUR_SPAN * float(std::min(width, height));
+    return std::clamp(blur, 0.f, 1.f) * std::min(span, SOURCE_BLUR_MAX_PX);
+}
+
+DecodedHeightTexture downscale_height_texture(const DecodedHeightTexture &src, int max_px)
+{
+    if (src.empty() || max_px <= 0 || (src.width <= max_px && src.height <= max_px))
+        return src;
+
+    const int  scale = std::max(1, (std::max(src.width, src.height) + max_px - 1) / max_px);
+    const int  w     = std::max(1, src.width / scale);
+    const int  h     = std::max(1, src.height / scale);
+    const bool color = src.has_color();
+
+    DecodedHeightTexture out;
+    out.width  = w;
+    out.height = h;
+    out.pixels.resize(size_t(w) * size_t(h));
+    if (color)
+        out.rgb.resize(size_t(w) * size_t(h) * 3);
+
+    tbb::parallel_for(tbb::blocked_range<int>(0, h), [&](const tbb::blocked_range<int> &r) {
+        for (int y = r.begin(); y < r.end(); ++y)
+            for (int x = 0; x < w; ++x) {
+                // The source block this destination texel covers. The max() keeps the block non-empty
+                // when rounding would otherwise collapse it.
+                const int x0 = x * src.width / w, x1 = std::max(x0 + 1, (x + 1) * src.width / w);
+                const int y0 = y * src.height / h, y1 = std::max(y0 + 1, (y + 1) * src.height / h);
+                uint32_t  sum_h = 0, sum_c[3] = { 0, 0, 0 }, n = 0;
+                for (int sy = y0; sy < y1 && sy < src.height; ++sy)
+                    for (int sx = x0; sx < x1 && sx < src.width; ++sx, ++n) {
+                        const size_t si = size_t(sy) * size_t(src.width) + size_t(sx);
+                        sum_h += src.pixels[si];
+                        if (color)
+                            for (int c = 0; c < 3; ++c)
+                                sum_c[c] += src.rgb[si * 3 + size_t(c)];
+                    }
+                const size_t di = size_t(y) * size_t(w) + size_t(x);
+                out.pixels[di]  = n > 0 ? uint8_t(sum_h / n) : 0;
+                if (color)
+                    for (int c = 0; c < 3; ++c)
+                        out.rgb[di * 3 + size_t(c)] = n > 0 ? uint8_t(sum_c[c] / n) : 0;
+            }
+    });
+    return out;
+}
+
+DecodedHeightTexture apply_texture_adjustments(const DecodedHeightTexture &src, const TextureAdjustments &adj)
+{
+    DecodedHeightTexture out = src;
+    if (src.empty() || adj.identity())
+        return out;
+
+    const int    w = out.width;
+    const int    h = out.height;
+    const size_t n = size_t(w) * size_t(h);
+
+    const float brightness = std::clamp(adj.brightness, -1.f, 1.f);
+    // Short of 1, so apply_contrast()'s gain stays finite; at this value it is already a 1000x slope,
+    // i.e. a threshold in all but name.
+    const float contrast   = std::clamp(adj.contrast, -1.f, 0.999f);
+    const float blur       = std::clamp(adj.blur, 0.f, 1.f);
+    const float sharpness  = std::clamp(adj.sharpness, 0.f, 1.f);
+
+    // The tonal pass: a 256-entry lookup table, because brightness and contrast are the same scalar
+    // curve for every texel and every channel. Building it once beats evaluating two curves a few
+    // million times, and it is what keeps this pass off the panel's critical path.
+    std::array<uint8_t, 256> tone{};
+    for (int i = 0; i < 256; ++i) {
+        float v = float(i) / 255.f;
+        v       = apply_brightness(v, brightness);
+        v       = apply_contrast(v, contrast);
+        tone[size_t(i)] = uint8_t(std::lround(std::clamp(v, 0.f, 1.f) * 255.f));
+    }
+
+    if (!out.has_color()) {
+        // Grayscale: one channel, and hue has nothing to turn.
+        tbb::parallel_for(tbb::blocked_range<size_t>(0, n), [&](const tbb::blocked_range<size_t> &r) {
+            for (size_t i = r.begin(); i < r.end(); ++i)
+                out.pixels[i] = tone[out.pixels[i]];
+        });
+        adjust_channel_spatial(out.pixels, w, h, blur, sharpness);
+        return out;
+    }
+
+    // Colour: tone each channel through the same table, then rotate the hue about the luminance axis.
+    //
+    // The rotation is feColorMatrix's hueRotate matrix (SVG filters), which holds Rec.709 luma fixed.
+    // The height below is taken with decode_height_texture()'s Rec.601 coefficients instead, so a hue
+    // turn is not perfectly height-neutral - a few levels at full saturation. Reconciling the two would
+    // mean a different rotation than every other tool's, which is the worse trade: the user is watching
+    // the colour, and the height follows the colour by construction either way.
+    const float  theta = adj.hue_deg * float(M_PI) / 180.f;
+    const float  c     = std::cos(theta);
+    const float  s     = std::sin(theta);
+    const float  m[9]  = {
+        0.213f + c * 0.787f - s * 0.213f, 0.715f - c * 0.715f - s * 0.715f, 0.072f - c * 0.072f + s * 0.928f,
+        0.213f - c * 0.213f + s * 0.143f, 0.715f + c * 0.285f + s * 0.140f, 0.072f - c * 0.072f - s * 0.283f,
+        0.213f - c * 0.213f - s * 0.787f, 0.715f - c * 0.715f + s * 0.715f, 0.072f + c * 0.928f + s * 0.072f,
+    };
+    const bool turn_hue = adj.hue_deg != 0.f;
+
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, n), [&](const tbb::blocked_range<size_t> &r) {
+        for (size_t i = r.begin(); i < r.end(); ++i) {
+            const float rr = float(tone[out.rgb[i * 3]]);
+            const float gg = float(tone[out.rgb[i * 3 + 1]]);
+            const float bb = float(tone[out.rgb[i * 3 + 2]]);
+            const float nr = turn_hue ? m[0] * rr + m[1] * gg + m[2] * bb : rr;
+            const float ng = turn_hue ? m[3] * rr + m[4] * gg + m[5] * bb : gg;
+            const float nb = turn_hue ? m[6] * rr + m[7] * gg + m[8] * bb : bb;
+            out.rgb[i * 3]     = uint8_t(std::lround(std::clamp(nr, 0.f, 255.f)));
+            out.rgb[i * 3 + 1] = uint8_t(std::lround(std::clamp(ng, 0.f, 255.f)));
+            out.rgb[i * 3 + 2] = uint8_t(std::lround(std::clamp(nb, 0.f, 255.f)));
+        }
+    });
+
+    // The spatial pass wants one channel at a time (smooth_height_pixels() is a single-channel blur, and
+    // reusing it is what keeps this consistent with Smoothing), so de-interleave, filter, re-interleave.
+    if (blur > 0.f || sharpness > 0.f) {
+        std::vector<uint8_t> channel(n);
+        for (int ch = 0; ch < 3; ++ch) {
+            for (size_t i = 0; i < n; ++i)
+                channel[i] = out.rgb[i * 3 + size_t(ch)];
+            adjust_channel_spatial(channel, w, h, blur, sharpness);
+            for (size_t i = 0; i < n; ++i)
+                out.rgb[i * 3 + size_t(ch)] = channel[i];
+        }
+    }
+
+    // Height is the luminance of the colour that came out, not the toned luminance of the colour that
+    // went in: the two differ once hue rotation or a per-channel clamp has moved the channels around,
+    // and a height that disagrees with the colour it is stored next to is the bug this avoids.
+    tbb::parallel_for(tbb::blocked_range<size_t>(0, n), [&](const tbb::blocked_range<size_t> &r) {
+        for (size_t i = r.begin(); i < r.end(); ++i)
+            out.pixels[i] = uint8_t(std::lround(0.299 * out.rgb[i * 3] + 0.587 * out.rgb[i * 3 + 1] +
+                                                0.114 * out.rgb[i * 3 + 2]));
+    });
+    return out;
+}
+
 TextureDetail analyze_texture_detail(const TextureDisplacementLayer &layer)
 {
     TextureDetail out;
@@ -491,57 +742,6 @@ V2Resolution recommend_v2_resolution(const indexed_triangle_set
     return out;
 }
 
-namespace {
-// Which side of a world plane a face is on, with an exactly zero component counted as the positive
-// side. The tie never shows: a normal component of zero carries zero tri-planar blend weight (see
-// triplanar_weights()), so the plane it orients contributes nothing at that point.
-inline float box_face_sign(float n) { return n >= 0.f ? 1.f : -1.f; }
-
-// The box projection's 2D basis for one of the three world planes, oriented the way a viewer
-// standing outside the model sees that face.
-//
-// v runs *down* the image, because that is what v means to the sampler: v = 0 is the texture's first
-// pixel row, i.e. its top (DecodedHeightTexture::sample(); the UV editor negates Y on screen for the
-// same reason, see UVEditorCanvas::render()). So v = -z on the four upright planes and v = -y on the
-// horizontal one, which is what puts the top of an image at the top of the model rather than
-// upside down.
-//
-// u then has to depend on which *side* of the plane the face is on, or one of the two faces sharing
-// a plane comes out left-right mirrored: with a single u per plane, a portrait image reads upright on
-// +X and 180 degrees round on -X. Fixing that is the sign below, chosen so that u x v == -normal,
-// i.e. (right, down, into the surface) is right-handed for a viewer outside:
-//
-//   face  u     v       face  u     v       face  u     v
-//   +X    +y    -z      +Y    -x    -z      +Z    +x    -y
-//   -X    -y    -z      -Y    +x    -z      -Z    -x    -y
-//
-// The sign flips where its own normal component crosses zero, and the blend weight of the plane it
-// belongs to is exactly zero there, so the blended tri-planar sum stays continuous across the flip -
-// it is not a return of the hard axis switch described on TextureProjectionMethod::Triplanar.
-inline Vec2f box_plane_yz(const Vec3f &p, float nx) { return Vec2f(box_face_sign(nx) * p.y(), -p.z()); }
-inline Vec2f box_plane_xz(const Vec3f &p, float ny) { return Vec2f(-box_face_sign(ny) * p.x(), -p.z()); }
-inline Vec2f box_plane_xy(const Vec3f &p, float nz) { return Vec2f(box_face_sign(nz) * p.x(), -p.y()); }
-} // namespace
-
-void box_projection_axes(const Vec3f &normal, Vec3f &u_axis, Vec3f &v_axis)
-{
-    // The same table as box_plane_yz()/box_plane_xz()/box_plane_xy(), handed out as a pair of world
-    // directions for the plane the normal is closest to. Two shapes of one table, because the bake's
-    // hot path wants the closed form and the GUI wants the axes; the test suite checks them against
-    // each other so they cannot drift apart.
-    const Vec3f n = normal.cwiseAbs();
-    if (n.x() >= n.y() && n.x() >= n.z()) {
-        u_axis = box_face_sign(normal.x()) * Vec3f::UnitY();
-        v_axis = -Vec3f::UnitZ();
-    } else if (n.y() >= n.x() && n.y() >= n.z()) {
-        u_axis = -box_face_sign(normal.y()) * Vec3f::UnitX();
-        v_axis = -Vec3f::UnitZ();
-    } else {
-        u_axis = box_face_sign(normal.z()) * Vec3f::UnitX();
-        v_axis = -Vec3f::UnitY();
-    }
-}
-
 Vec2f project_planar(const Vec3f &position, const Vec3f &normal)
 {
     // Planar-project onto the two axes orthogonal to the dominant component of `normal`. Called
@@ -552,26 +752,23 @@ Vec2f project_planar(const Vec3f &position, const Vec3f &normal)
     // other face in the same patch - exactly the bug an earlier version of this feature had).
     const Vec3f n = normal.cwiseAbs();
     if (n.x() >= n.y() && n.x() >= n.z())
-        return box_plane_yz(position, normal.x());
+        return Vec2f(position.y(), position.z());
     if (n.y() >= n.x() && n.y() >= n.z())
-        return box_plane_xz(position, normal.y());
-    return box_plane_xy(position, normal.z());
+        return Vec2f(position.x(), position.z());
+    return Vec2f(position.x(), position.y());
 }
 
 namespace {
 // Wrapped around patch_axis, centered at patch_center. u is the arc length (mm) around the axis at
-// this point's own radius, v is the distance along the axis, measured *against* it - a reasonable
-// approximation for roughly cylindrical selections, not an exact fit for arbitrary geometry.
+// this point's own radius, v is the signed distance along the axis - a reasonable approximation
+// for roughly cylindrical selections, not an exact fit for arbitrary geometry.
 Vec2f project_cylindrical(const Vec3f &position, const Vec3f &patch_center, const Vec3f &patch_axis)
 {
     Vec3f up = patch_axis;
     up       = (up.norm() > 1e-8f) ? Vec3f(up.normalized()) : Vec3f::UnitZ();
     const Vec3f arbitrary = (std::abs(up.dot(Vec3f::UnitZ())) < 0.9f) ? Vec3f::UnitZ() : Vec3f::UnitX();
     const Vec3f right     = Vec3f(up.cross(arbitrary).normalized());
-    // up x right, not right x up: that makes (right, fwd, up) right-handed, so the angle below grows
-    // anticlockwise about the axis - which, seen from outside the cylinder, is to the viewer's right.
-    // The other way round the texture wraps on mirrored, as if seen through the model from behind.
-    const Vec3f fwd       = Vec3f(up.cross(right).normalized());
+    const Vec3f fwd       = Vec3f(right.cross(up).normalized());
 
     const Vec3f rel        = position - patch_center;
     const float along_axis = rel.dot(up);
@@ -580,9 +777,7 @@ Vec2f project_cylindrical(const Vec3f &position, const Vec3f &patch_center, cons
     const float radius     = std::sqrt(x * x + y * y);
     const float angle      = std::atan2(y, x);
 
-    // Negated, like every other projection's v: v = 0 is the texture's top row, so v has to grow
-    // *down* the axis for the top of the image to sit at the top of the model.
-    return Vec2f(angle * radius, -along_axis);
+    return Vec2f(angle * radius, along_axis);
 }
 
 // Longitude/latitude around patch_center. u/v are scaled by this point's own distance from the
@@ -598,9 +793,7 @@ Vec2f project_spherical(const Vec3f &position, const Vec3f &patch_center)
     const Vec3f dir       = rel / radius;
     const float longitude = std::atan2(dir.y(), dir.x());
     const float latitude  = std::asin(std::clamp(dir.z(), -1.f, 1.f));
-    // Longitude already grows to the right as seen from outside; latitude grows toward the north
-    // pole, so it is negated to put the image's top row (v = 0) at the top of the model.
-    return Vec2f(longitude, -latitude) * radius;
+    return Vec2f(longitude, latitude) * radius;
 }
 
 // CGAL's LSCM parameterizer expects a clean mesh with no isolated (unreferenced) vertices - but
@@ -895,26 +1088,9 @@ std::vector<int> segment_into_charts(const indexed_triangle_set &mesh, const std
 // solve at all, and why this also serves as the fallback for a chart LSCM cannot handle.
 std::vector<Vec2f> project_to_tangent_plane(const indexed_triangle_set &chart, const Vec3f &normal)
 {
-    // Oriented like the box projection (see box_projection_axes()), so a chart reads the right way up
-    // and unmirrored instead of being flattened to whichever basis a cross product happened to give.
-    // For a chart whose normal *is* a world axis - a cube face, which is the common case once the
-    // seam angle has cut the patch along its sharp edges - this is exactly the box basis, so such a
-    // face unwraps to the same orientation Triplanar would have given it.
-    Vec3f u, v;
-    box_projection_axes(normal, u, v);
-    // The box axes lie in the tangent plane already when the normal is a world axis; for any other
-    // normal, u is squared up against it and v follows. u x v == -normal keeps the chart the way
-    // round a viewer outside the model sees it (a plain normal x u would mirror it).
-    u = u - normal * normal.dot(u);
-    if (u.norm() <= 1e-6f) {
-        // Out of reach for a unit normal - the box basis puts u perpendicular to the normal's own
-        // dominant axis, so the two can never be within 45 degrees of each other - but a caller
-        // handing over an unnormalized normal should still get a usable basis rather than a NaN.
-        const Vec3f seed = (std::abs(normal.z()) < 0.9f) ? Vec3f::UnitZ() : Vec3f::UnitX();
-        u = seed.cross(normal);
-    }
-    u = Vec3f(u.normalized());
-    v = Vec3f(u.cross(normal).normalized());
+    const Vec3f seed = (std::abs(normal.z()) < 0.9f) ? Vec3f::UnitZ() : Vec3f::UnitX();
+    const Vec3f u    = Vec3f(seed.cross(normal).normalized());
+    const Vec3f v    = Vec3f(normal.cross(u).normalized());
 
     std::vector<Vec2f> uvs(chart.vertices.size());
     for (size_t i = 0; i < chart.vertices.size(); ++i)
@@ -1889,10 +2065,8 @@ float sample_layer_height(const DecodedHeightTexture &texture, const TextureDisp
             return texture.sample(uv, layer.tile_enabled, layer.tile_method);
         }
         // Flat projection onto the captured projector plane. Single-valued per point, so unlike
-        // blended triplanar it is one sample, and it is what "project from view" places. The
-        // projector's up axis is negated because v runs *down* the image (v = 0 is its first pixel
-        // row), the same reason the projective branch above measures window y downward.
-        return sample_at(Vec2f(position.dot(layer.view_project_right), -position.dot(layer.view_project_up)));
+        // blended triplanar it is one sample, and it is what "project from view" places.
+        return sample_at(Vec2f(position.dot(layer.view_project_right), position.dot(layer.view_project_up)));
     case TextureProjectionMethod::LSCM: // no usable unwrap for this patch - fall back to Triplanar
     case TextureProjectionMethod::Triplanar:
     default: break;
@@ -1907,15 +2081,14 @@ float sample_layer_height(const DecodedHeightTexture &texture, const TextureDisp
     const float w_sum = w.x() + w.y() + w.z();
     if (w_sum < 1e-8f)
         // Degenerate normal: no axis is meaningfully dominant, so no blend is meaningful either.
-        return sample_at(box_plane_xy(position, normal.z()));
+        return sample_at(Vec2f(position.x(), position.y()));
     w /= w_sum;
 
-    // Each plane drops the axis it is named for and is oriented for the side of that plane the normal
-    // points to, matching project_planar()'s own convention (which the GUI's on-canvas placement
-    // gizmo also relies on). See box_plane_yz() for why the orientation is not simply (y, z).
-    return w.x() * sample_at(box_plane_yz(position, normal.x())) +
-           w.y() * sample_at(box_plane_xz(position, normal.y())) +
-           w.z() * sample_at(box_plane_xy(position, normal.z()));
+    // Each plane drops the axis it is named for, matching project_planar()'s own convention (which
+    // the GUI's on-canvas placement gizmo also relies on).
+    return w.x() * sample_at(Vec2f(position.y(), position.z())) +
+           w.y() * sample_at(Vec2f(position.x(), position.z())) +
+           w.z() * sample_at(Vec2f(position.x(), position.y()));
 }
 
 bool sample_layer_color(const DecodedHeightTexture &texture, const TextureDisplacementLayer &layer,
@@ -1977,8 +2150,7 @@ bool sample_layer_color(const DecodedHeightTexture &texture, const TextureDispla
             out = texture.sample_color(uv, layer.tile_enabled, layer.tile_method);
             return true;
         } else {
-            // Negated up, exactly as sample_layer_height() does it.
-            const Vec2f p(position.dot(layer.view_project_right), -position.dot(layer.view_project_up));
+            const Vec2f p(position.dot(layer.view_project_right), position.dot(layer.view_project_up));
             if (!covered(p))
                 return false;
             out = sample_at(p);
@@ -1994,7 +2166,7 @@ bool sample_layer_color(const DecodedHeightTexture &texture, const TextureDispla
     Vec3f w = triplanar_weights(normal);
     const float w_sum = w.x() + w.y() + w.z();
     if (w_sum < 1e-8f) {
-        const Vec2f p = box_plane_xy(position, normal.z());
+        const Vec2f p(position.x(), position.y());
         if (!covered(p))
             return false;
         out = sample_at(p);
@@ -2005,8 +2177,8 @@ bool sample_layer_color(const DecodedHeightTexture &texture, const TextureDispla
     // A blend of three planes is only "not covered" where *every* contributing plane is outside the
     // placement; where some are, the covered ones are renormalised so the colour does not fade toward
     // black at the edge of an untiled tri-planar layer.
-    const std::array<Vec2f, 3> planes = { box_plane_yz(position, normal.x()), box_plane_xz(position, normal.y()),
-                                          box_plane_xy(position, normal.z()) };
+    const std::array<Vec2f, 3> planes = { Vec2f(position.y(), position.z()), Vec2f(position.x(), position.z()),
+                                          Vec2f(position.x(), position.y()) };
     Vec3f acc     = Vec3f::Zero();
     float acc_w   = 0.f;
     for (int i = 0; i < 3; ++i)

src/libslic3r/TextureDisplacement.hpp

@@ -154,6 +154,38 @@ struct TextureIsland
 // chart to its true mm area, so a freshly unwrapped patch has uniform texel density to begin with.
 void average_island_scales(std::vector<TextureIsland> &islands);
 
+// Photo-style adjustments to a layer's source image, as the gizmo's image-adjustment panel sets them.
+//
+// These are *not* layer parameters: nothing here is stored on TextureDisplacementLayer and nothing here is
+// re-applied at bake time. The panel applies them once, to the image, and the result becomes the layer's
+// image - so the adjusted pixels feed the colour and the displacement together, and a brightness change
+// really does change the relief. That is the intended behaviour: one image, one source of truth, rather
+// than a second set of knobs the bake would have to replay in the right order.
+//
+// Contrast with TextureDisplacementLayer::smoothing, which *is* a layer parameter applied on every decode:
+// `blur` here is a destructive edit of the image, `smoothing` is a live low-pass over whatever the image is.
+struct TextureAdjustments
+{
+    float brightness = 0.f; // [-1, 1]; 0 unchanged, -1 black, +1 white
+    float contrast   = 0.f; // [-1, 1]; 0 unchanged, -1 flat mid-grey, +1 hard threshold
+    float sharpness  = 0.f; // [0, 1];  0 unchanged. Unsharp-mask amount
+    float blur       = 0.f; // [0, 1];  0 unchanged. Fraction of SOURCE_BLUR_SPAN, as `smoothing` is
+    float hue_deg    = 0.f; // [-180, 180]; 0 unchanged. No effect on a grayscale image - grey has no hue
+
+    bool identity() const
+    {
+        return brightness == 0.f && contrast == 0.f && sharpness == 0.f && blur == 0.f && hue_deg == 0.f;
+    }
+    // Exact equality, which is what is wanted: these come straight off sliders, and the question asked of
+    // them is "is this still the value the preview on screen was computed from", not "are these close".
+    bool operator==(const TextureAdjustments &o) const
+    {
+        return brightness == o.brightness && contrast == o.contrast && sharpness == o.sharpness &&
+               blur == o.blur && hue_deg == o.hue_deg;
+    }
+    bool operator!=(const TextureAdjustments &o) const { return !(*this == o); }
+};
+
 // One texture asset plus its projection/displacement parameters. Several layers may be painted
 // onto overlapping areas of the same volume: their displacements are combined per vertex, in slot
 // order, each layer folding into the total via its own TextureBlendMode (see
@@ -277,6 +309,18 @@ struct TextureDisplacementLayer
     //  - zero or positive: a mesh vertex, every unwrapped copy of it (how edits were stored before).
     std::vector<std::pair<int, Vec2f>> lscm_uv_overrides;
 
+    // Live, unsaved image adjustments from the gizmo's image-adjustment panel, applied by
+    // decode_height_texture() on top of the decoded image - so while the panel is open the relief, the
+    // colour, the thumbnails and the bake all see the adjusted image, and moving a slider really does
+    // change the displacement. See TextureAdjustments.
+    //
+    // Deliberately *not* serialized, by either save()/load() here or the .3mf: it is the state of an open
+    // editor, not a property of the layer. The panel resets it when it closes, and "Save as copy" resolves
+    // it by writing a new image and pointing the layer at that - which is the only way an adjustment
+    // becomes permanent. A project saved mid-adjustment therefore stores the unadjusted image, which is
+    // the honest answer: nothing was committed.
+    TextureAdjustments preview_adjust;
+
     // How this layer folds into the displacement accumulated by the layers below it. Ignored for
     // the lowest-slot painted layer, which has nothing beneath it to combine with (the GUI shows
     // it as the "Base" layer and hides the control).
@@ -477,6 +521,36 @@ struct DecodedHeightTexture
     bool texel_tap(const Vec2f &uv, bool tile_enabled, TextureTileMethod tile_method, TexelTap &out) const;
 };
 
+// Applies `adj` to `src` and returns the result; `src` is left alone. An empty `src`, or an identity
+// `adj`, gives back a copy.
+//
+// Order is tonal, then spatial: brightness, contrast and hue per texel first, then blur, then sharpness.
+// Sharpness last is what lets the two spatial knobs be used together - blur to kill speckle, then
+// sharpness to put the real edges back - instead of the blur simply undoing the sharpen.
+//
+// Grayscale in, grayscale out (`rgb` stays empty): promoting a grey image to RGB would hand the layer's
+// colour feature a row of identical greys to "colour" the model with, and triple the stored PNG for it.
+// For a colour image the height is recomputed as the luminance of the *adjusted* colour, with
+// decode_height_texture()'s own coefficients, so the relief and the colour can never drift apart.
+DecodedHeightTexture apply_texture_adjustments(const DecodedHeightTexture &src, const TextureAdjustments &adj);
+
+// Blur radius, in texels, that TextureAdjustments::blur == 1 means on a `min(width, height)`-sized image:
+// the same 5%-of-the-short-side span the Smoothing slider uses, under the same 48-texel cost cap, so the
+// two controls bite at the same rate and a user moving between them is not surprised.
+float adjustment_blur_radius(float blur, int width, int height);
+
+// Box-filters `src` down so neither side exceeds `max_px`, preserving aspect; never upscales, and
+// returns a copy when it already fits. Colour and height are filtered the same way, and the height
+// stays the height - it is not recomputed from the filtered colour, because a box filter is linear and
+// luminance is linear in the channels, so the two agree already.
+//
+// This is what lets the adjustment panel's live preview cost depend on the size of the box it is drawn
+// in rather than on the size of the image: adjusting a downscaled copy per slider frame, and the
+// full-size image only once, on commit. A box filter (rather than a plain decimation) is the point -
+// these textures are high-frequency by nature, and dropping texels would alias the preview into
+// showing detail the adjustment is not actually producing.
+DecodedHeightTexture downscale_height_texture(const DecodedHeightTexture &src, int max_px);
+
 // Decode a layer's raw image bytes into sampleable height data, plus colour when the source has any.
 // Both 8-bit grayscale PNGs (the shipped library, and anything imported before colour was kept) and
 // colour PNGs are accepted; for a colour source the height is its luminance, using the same
@@ -524,24 +598,11 @@ struct TextureColorSettings
     bool empty() const { return palette.empty(); }
 };
 
-// The two world directions the box projection takes its u and v along on a face whose outward
-// normal is `normal`: the plane is the one that normal is closest to, and the pair is oriented as a
-// viewer standing outside the model sees it - u to their right, v *down* the image, which is the
-// direction v runs in the texture (v = 0 is the image's first pixel row, see
-// DecodedHeightTexture::sample()). So an image comes out the way it looks in a file manager rather
-// than upside down, and it is not mirrored on the three faces facing the other way.
-//
-// Exposed because the GUI needs the same basis for the on-canvas "adjust texture placement" gizmo
-// (its ring's zero angle and its offset handle's plane), and it must not be a second, drifting copy
-// of the table.
-void box_projection_axes(const Vec3f &normal, Vec3f &u_axis, Vec3f &v_axis);
-
 // Raw dominant-axis planar projection of `position` (in mm, not yet scaled/rotated/offset by any
-// layer), dropping the axis position that best aligns with `normal`. Equivalent to projecting onto
-// box_projection_axes()' pair. Exposed on its own (rather than only inline inside
-// project_texture_displacement_uv()) so GUI code - the on-canvas "adjust texture placement" gizmo -
-// can map a dragged 3D point into the exact same 2D space tiling_scale/rotation_deg/offset operate
-// in, without duplicating the axis-selection logic.
+// layer), dropping the axis position that best aligns with `normal`. Exposed on its own (rather
+// than only inline inside project_texture_displacement_uv()) so GUI code - the on-canvas
+// "adjust texture placement" gizmo - can map a dragged 3D point into the exact same 2D space
+// tiling_scale/rotation_deg/offset operate in, without duplicating the axis-selection logic.
 Vec2f project_planar(const Vec3f &position, const Vec3f &normal);
 
 // Applies a layer's tiling_scale/rotation_deg/offset to an already-projected planar coordinate

src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.cpp

@@ -43,6 +43,7 @@
 #include <cstdint>
 #include <functional>
 #include <chrono>
+#include <future>
 #include <cstdio>
 #include <glad/gl.h>
 #include <imgui.h>
@@ -120,6 +121,14 @@ constexpr int THUMBNAIL_MAX_PX = 128;
 // blur of it - which is what made Fast look flatter and softer than the result it was previewing.
 constexpr int HEIGHT_TEX_MAX_PX = 2048;
 
+// Size the image-adjustment panel's live preview is computed and uploaded at. The panel draws the image
+// in a box about 240 px wide, so there is nothing to show above this - and the preview is recomputed on
+// every slider move, which is what makes its cost worth bounding. Measured on a 1024x1024 with every
+// knob engaged, a full-size pass is 13-19 ms grayscale / 40-60 ms in colour (130-190 ms at 2048 in
+// colour); the same pass on a 384 px copy is 3-4 ms / 9-12 ms, and it runs off the UI thread besides.
+// The full-size image is only ever adjusted once, on commit.
+constexpr int ADJUST_PREVIEW_MAX_PX = 384;
+
 // How many rings of vertex-adjacent triangles either side of the paint's edge join the border refine
 // band (see collect_paint_region()). Two is enough to grade the size change without the band's own
 // cost growing to matter: it is a ring around a perimeter, not an area.
@@ -525,6 +534,10 @@ void GLGizmoTextureDisplacement::on_shutdown()
     // progress poll, and its completion handler then finds nothing to do.
     m_preview_generation->fetch_add(1);
     m_preview_job_pending = false;
+    // The adjustment panel holds a full-size decode of its layer's image, which is the largest thing
+    // here; a closed gizmo should not keep it alive. Discards the edit, as closing the gizmo on an open
+    // panel implies.
+    close_image_adjust();
     // The palette caches hold the last volume's images; a closed gizmo should not keep them alive.
     m_palette_cache.clear();
     m_palette_quantizer      = nullptr;
@@ -1252,9 +1265,8 @@ std::vector<Vec2f> GLGizmoTextureDisplacement::compute_layer_vertex_uvs(const in
                     uv[vi] = Vec2f(-1e6f, -1e6f);
                 continue;
             }
-            // Negated up, as sample_layer_height()'s affine branch has it: v runs down the image.
             const Vec2f planar(patch.vertices[vi].dot(layer.view_project_right),
-                               -patch.vertices[vi].dot(layer.view_project_up));
+                               patch.vertices[vi].dot(layer.view_project_up));
             uv[vi] = apply_uv_transform(planar, layer, aspect);
         }
         return uv;
@@ -2451,9 +2463,12 @@ void GLGizmoTextureDisplacement::update_uv_editor()
     // before, and independently of, the unwrap - the texture belongs on screen before anything is unwrapped - and
     // only when the choice, the layer's image or its smoothing changed, because the height image is large.
     const UVBackground desired_bg = (m_uv_check_mode == UVCheckMode::Checker) ? UVBackground::Checker : UVBackground::Height;
-    const bool bg_smoothing_changed = (desired_bg == UVBackground::Height) && (m_uv_editor_bg_smoothing != layer->smoothing);
+    const bool bg_smoothing_changed = (desired_bg == UVBackground::Height) &&
+                                      (m_uv_editor_bg_smoothing != layer->smoothing ||
+                                       !(m_uv_editor_bg_adjust == layer->preview_adjust));
     if (desired_bg != m_uv_editor_bg || layer->image_data.get() != m_uv_editor_bg_image || bg_smoothing_changed) {
         m_uv_editor_bg_smoothing = layer->smoothing;
+        m_uv_editor_bg_adjust    = layer->preview_adjust;
         m_uv_editor_bg_image     = layer->image_data.get();
         m_uv_editor_bg           = desired_bg;
         if (desired_bg == UVBackground::Checker) {
@@ -3293,10 +3308,19 @@ Vec3f GLGizmoTextureDisplacement::adjust_handle_center(const TextureDisplacement
 
 void GLGizmoTextureDisplacement::adjust_tangent_basis(Vec3f &u_axis, Vec3f &v_axis) const
 {
-    // libslic3r's own basis, asked for rather than restated here, so the ring's "0 degrees" and the
-    // offset handle's plane always agree with what project_texture_displacement_uv() does - including
-    // v pointing *down* the texture and u flipping on the far side of each plane.
-    box_projection_axes(m_adjust_anchor_normal, u_axis, v_axis);
+    // Mirrors project_planar()'s own dominant-axis choice exactly, so the ring's "0 degrees" and
+    // the offset handle's plane always agree with what project_texture_displacement_uv() does.
+    const Vec3f n = m_adjust_anchor_normal.cwiseAbs();
+    if (n.x() >= n.y() && n.x() >= n.z()) {
+        u_axis = Vec3f::UnitY();
+        v_axis = Vec3f::UnitZ();
+    } else if (n.y() >= n.x() && n.y() >= n.z()) {
+        u_axis = Vec3f::UnitX();
+        v_axis = Vec3f::UnitZ();
+    } else {
+        u_axis = Vec3f::UnitX();
+        v_axis = Vec3f::UnitY();
+    }
 }
 
 void GLGizmoTextureDisplacement::render_adjust_texture_gizmo()
@@ -3664,6 +3688,7 @@ void GLGizmoTextureDisplacement::ensure_panel_icons()
         "texture_displacement_checker.svg", "texture_displacement_distortion.svg",
         "texture_displacement_wireframe.svg", "texture_displacement_cross.svg",
         "texture_displacement_uv_select_island.svg", "texture_displacement_uv_select_edge.svg",
+        "cog.svg", // the layer card's "adjust image" button
         "texture_displacement_uv_select_vertex.svg",
         // Paint / Erase, brush cursor shape, mapping, tiling, placement and the dock toggle.
         "texture_displacement_add.svg", "texture_displacement_add_negative.svg", "circle_paint.svg",
@@ -3974,6 +3999,338 @@ void GLGizmoTextureDisplacement::render_texture_library_popup(const ImVec2 &pane
         m_picker_open_request = true;
     }
 }
+bool GLGizmoTextureDisplacement::load_image_adjust_source(const TextureDisplacementLayer &layer)
+{
+    if (layer.empty())
+        return false;
+
+    // The *raw* image: neither the layer's Smoothing nor the panel's own preview_adjust, so what the
+    // sliders act on is always the image as it is actually stored rather than the last preview of it.
+    // Without clearing preview_adjust here the adjustment would compound on itself every reload.
+    TextureDisplacementLayer raw = layer;
+    raw.smoothing                = 0.f;
+    raw.preview_adjust           = TextureAdjustments{};
+
+    DecodedHeightTexture decoded = decode_height_texture(raw);
+    if (decoded.empty())
+        return false;
+
+    m_adjust_source         = std::move(decoded);
+    m_adjust_preview_source = downscale_height_texture(m_adjust_source, ADJUST_PREVIEW_MAX_PX);
+    m_adjust_source_image   = layer.image_data.get();
+    // The unadjusted image, so the box is filled now rather than one background pass later. Pairing it
+    // with an identity `shown` is what makes update_image_adjust_preview() relaunch for the sliders'
+    // current values against the new source instead of deciding it is already showing them.
+    m_adjust_preview_shown = TextureAdjustments{};
+    m_adjust_preview_tex   = upload_height_thumbnail(m_adjust_preview_source, ADJUST_PREVIEW_MAX_PX);
+    m_adjust_preview_valid = m_adjust_preview_tex != nullptr;
+    return true;
+}
+
+void GLGizmoTextureDisplacement::open_image_adjust(const TextureDisplacementLayer &layer)
+{
+    if (layer.empty() || layer.slot < 0)
+        return;
+
+    close_image_adjust(); // reverts and clears any previous panel
+
+    if (!load_image_adjust_source(layer))
+        return;
+
+    m_adjust           = TextureAdjustments{};
+    m_adjust_applied   = TextureAdjustments{};
+    m_adjust_slot      = layer.slot;
+    const ModelVolume *mv = texture_volume();
+    m_adjust_volume_id = mv != nullptr ? mv->id().id : 0;
+}
+
+void GLGizmoTextureDisplacement::invalidate_adjust_textures()
+{
+    // The GPU copies of a layer's image - the list thumbnail, the preview shader's height and colour
+    // textures - are keyed on the image_data pointer and the layer's Smoothing, and a live adjustment
+    // changes neither: the pointer still names the same PNG. Rather than widen three cache keys for a
+    // panel that is open a few seconds at a time, the panel drops the copies itself whenever it moves
+    // the adjustment. Nulling the source is enough; the next get_layer_*() rebuilds from the decode,
+    // which does see the adjustment.
+    m_thumbnail_source.fill(nullptr);
+    m_color_tex_source  = nullptr;
+    m_height_tex_source = nullptr;
+}
+
+void GLGizmoTextureDisplacement::close_image_adjust()
+{
+    // Revert the layer's live adjustment. Every exit that reaches here is a discard: a commit resets
+    // preview_adjust itself, before pointing the layer at the file that already carries the edit, so this
+    // cannot undo a committed adjustment.
+    //
+    // Found by the id recorded when the panel opened rather than through texture_volume(), which answers
+    // for the *current* selection. One of the ways to get here is the selection having moved on, and
+    // reverting the newly selected object's layer instead would both miss the adjustment that is still
+    // live on the original volume and clear one the user never touched.
+    bool reverted = false;
+    if (m_adjust_slot >= 0 && m_adjust_volume_id != 0)
+        for (ModelObject *mo : wxGetApp().model().objects) {
+            for (ModelVolume *mv : mo->volumes) {
+                if (mv->id().id != m_adjust_volume_id)
+                    continue;
+                for (TextureDisplacementLayer &l : mv->texture_displacement_layers)
+                    if (l.slot == m_adjust_slot && !l.preview_adjust.identity()) {
+                        l.preview_adjust = TextureAdjustments{};
+                        reverted         = true;
+                    }
+            }
+        }
+
+    if (reverted)
+        invalidate_adjust_textures();
+
+    // std::async's future blocks here until the pass finishes. That is a few milliseconds on an image
+    // this small, and the alternative - a detached thread writing into the members of a closed panel -
+    // is worse.
+    if (m_adjust_preview_job.valid())
+        m_adjust_preview_job.wait();
+    m_adjust_preview_job = {};
+
+    m_adjust_slot           = -1;
+    m_adjust                = TextureAdjustments{};
+    m_adjust_applied        = TextureAdjustments{};
+    m_adjust_source         = DecodedHeightTexture{};
+    m_adjust_preview_source = DecodedHeightTexture{};
+    m_adjust_source_image   = nullptr;
+    m_adjust_volume_id      = 0;
+    m_adjust_preview_tex.reset();
+    m_adjust_preview_valid = false;
+
+    // Only while the gizmo is up: on_shutdown() also comes through here, and rebuilding a preview for a
+    // gizmo that is closing would be work for a model nobody is looking at. The reverted layer data is
+    // what matters there, and that is already done above.
+    if (reverted && m_state == On) {
+        rebuild_preview();
+        m_parent.set_as_dirty();
+    }
+}
+
+void GLGizmoTextureDisplacement::update_image_adjust_preview()
+{
+    if (m_adjust_preview_source.empty())
+        return;
+
+    // Collect a finished pass. wait_for(0) rather than get() outright: this runs inside the frame, and
+    // blocking on the worker here would hand back to the UI thread the very stall the worker exists to
+    // spare it.
+    if (m_adjust_preview_job.valid() &&
+        m_adjust_preview_job.wait_for(std::chrono::seconds(0)) == std::future_status::ready) {
+        const DecodedHeightTexture adjusted = m_adjust_preview_job.get();
+        m_adjust_preview_job                = {};
+        if (std::unique_ptr<GLTexture> tex = upload_height_thumbnail(adjusted, ADJUST_PREVIEW_MAX_PX)) {
+            m_adjust_preview_tex   = std::move(tex);
+            m_adjust_preview_shown = m_adjust_preview_running;
+            m_adjust_preview_valid = true;
+        }
+    }
+
+    // One pass at a time: whatever the sliders did while it ran is picked up by the next launch, so a
+    // drag collapses to the value the sliders ended on instead of queuing one pass per frame.
+    if (!m_adjust_preview_job.valid() && m_adjust != m_adjust_preview_shown) {
+        m_adjust_preview_running = m_adjust;
+        // Captured by value: the pass must not read members the UI thread goes on editing while it runs.
+        m_adjust_preview_job = std::async(std::launch::async,
+                                          [src = m_adjust_preview_source, adj = m_adjust_preview_running] {
+                                              return apply_texture_adjustments(src, adj);
+                                          });
+    }
+
+    // A pass in flight has no other way to get its result on screen: without a redraw request the canvas
+    // can sit idle, and the preview would only catch up on the next unrelated frame.
+    if (m_adjust_preview_job.valid())
+        m_parent.set_as_dirty();
+}
+
+void GLGizmoTextureDisplacement::commit_image_adjust(TextureDisplacementLayer &layer)
+{
+    if (m_adjust_source.empty() || m_adjust.identity()) {
+        // Nothing was changed, so there is nothing to save.
+        close_image_adjust();
+        return;
+    }
+
+    // The full-size pass, once: 13-19 ms grayscale / 40-60 ms colour on a 1024x1024 with every knob
+    // engaged. Run on the UI thread deliberately, unlike the live preview: this is a single click, and the
+    // rebuild that follows it - a CPU mesh displacement of the painted patch - is already an order of
+    // magnitude more work, synchronously, so moving only this off the thread would buy nothing a user
+    // could perceive.
+    const DecodedHeightTexture adjusted = apply_texture_adjustments(m_adjust_source, m_adjust);
+
+    std::string                              error;
+    const std::string                        stem  = layer.name.empty() ? std::string("texture") : layer.name;
+    const std::optional<TextureLibraryEntry> entry = save_texture_to_library(adjusted, stem, error);
+    if (!entry) {
+        show_error(nullptr, error);
+        return; // the panel stays open, and the layer keeps the live adjustment: the edit is not lost
+    }
+
+    // Cleared *before* the layer is pointed at the new file, and this ordering is the whole correctness of
+    // the commit: the saved image already has the adjustment baked into its pixels, so leaving
+    // preview_adjust set would apply brightness, contrast and the rest a second time on top of itself.
+    layer.preview_adjust = TextureAdjustments{};
+    // set_layer_texture() does the rest - the name, the recently-used ordering, a fresh image_data buffer
+    // (which is what invalidates every cache keyed by the old pointer), the undo snapshot and the rebuild.
+    set_layer_texture(layer, *entry);
+
+    close_image_adjust();
+}
+
+void GLGizmoTextureDisplacement::render_image_adjust_window(const ImVec2 &panel_min, const ImVec2 &panel_max)
+{
+    if (m_adjust_slot < 0)
+        return;
+
+    ModelVolume *mv = texture_volume();
+    // A different volume is selected than the one this panel was opened on. Slots are numbered per
+    // volume, so looking m_adjust_slot up here would find an unrelated layer rather than nothing.
+    if (mv == nullptr || mv->id().id != m_adjust_volume_id) {
+        close_image_adjust();
+        return;
+    }
+
+    TextureDisplacementLayer *layer = nullptr;
+    for (TextureDisplacementLayer &l : mv->texture_displacement_layers)
+        if (l.slot == m_adjust_slot)
+            layer = &l;
+    if (layer == nullptr) {
+        // The layer went away under the panel (removed, or merged away by an undo).
+        close_image_adjust();
+        return;
+    }
+
+    // The layer's image can be swapped from the texture picker while this panel is open - the panel is a
+    // window now, so the rest of the gizmo stays usable behind it. Re-read the source when that happens,
+    // keeping the slider positions: the user is adjusting this layer, and the 3D view has already moved to
+    // the new image (decode_height_texture() reads layer.image_data, which changed), so re-reading here is
+    // also what keeps the panel's photo and the model showing the same thing.
+    if (layer->image_data.get() != m_adjust_source_image && !load_image_adjust_source(*layer)) {
+        close_image_adjust(); // the new image cannot be decoded; nothing left to adjust
+        return;
+    }
+
+    const float img_w = std::round(m_imgui->scaled(16.f));
+    const float gap   = m_imgui->scaled(0.5f);
+    // Placed beside the panel on first appearance only, and left wherever the user drags it after that -
+    // it is a window, not a popup, so its position is theirs to keep.
+    const float win_w = img_w + 2.f * ImGui::GetStyle().WindowPadding.x;
+    const bool  left  = panel_min.x - gap - win_w >= 0.f;
+    ImGui::SetNextWindowPos(ImVec2(left ? panel_min.x - gap - win_w : panel_max.x + gap,
+                                   panel_min.y + m_imgui->scaled(4.f)), ImGuiCond_Appearing);
+
+    bool keep_open = true;
+    if (!ImGui::Begin((_u8L("Adjust image") + "##texture_adjust").c_str(), &keep_open,
+                      ImGuiWindowFlags_AlwaysAutoResize | ImGuiWindowFlags_NoCollapse)) {
+        ImGui::End();
+        if (!keep_open)
+            close_image_adjust();
+        return;
+    }
+
+    // Collect a finished pass and start one for the current slider values before the image is drawn, so
+    // the newest available result is what lands on screen this frame.
+    update_image_adjust_preview();
+
+    // The photo itself, at the image's own aspect so a non-square texture is not stretched.
+    const float aspect = m_adjust_source.height > 0 ? float(m_adjust_source.width) / float(m_adjust_source.height) : 1.f;
+    const float img_h  = std::round(img_w / std::max(0.05f, aspect));
+    if (m_adjust_preview_valid && m_adjust_preview_tex)
+        ImGui::Image((ImTextureID) (intptr_t) m_adjust_preview_tex->get_id(), ImVec2(img_w, img_h));
+    else
+        ImGui::Dummy(ImVec2(img_w, img_h));
+
+    // The label column is sized off the widest of the five labels, so the tracks line up whatever the
+    // translation does to their lengths.
+    float label_w = 0.f;
+    for (const wxString &l : { _L("Brightness"), _L("Contrast"), _L("Sharpness"), _L("Blur"), _L("Hue") })
+        label_w = std::max(label_w, ImGui::CalcTextSize(into_u8(l).c_str()).x);
+    label_w += m_imgui->scaled(1.2f);
+    // An explicit track width rather than a fill-to-the-right one: this window is AlwaysAutoResize, so its
+    // width comes from its content, and an item asking for "whatever is left" would make the width depend
+    // on itself. The image above sets the content width, and the sliders match it.
+    const float slider_w = std::max(m_imgui->scaled(4.f), img_w - label_w);
+
+    const auto row = [&](const char *id, const wxString &label, float *v, float v_min, float v_max,
+                         const char *format, bool enabled, const std::string &tip) {
+        const float x0 = ImGui::GetCursorPosX();
+        ImGui::AlignTextToFramePadding();
+        m_imgui->text(label);
+        ImGui::SameLine();
+        ImGui::SetCursorPosX(std::max(ImGui::GetCursorPosX(), x0 + label_w));
+        ImGui::SetNextItemWidth(slider_w);
+        m_imgui->disabled_begin(!enabled);
+        ImGui::SliderFloat(id, v, v_min, v_max, format, ImGuiSliderFlags_AlwaysClamp);
+        m_imgui->disabled_end();
+        // Only on an enabled row: a disabled item does not report hover, so a tooltip on one would never
+        // be shown. What has to be said about a disabled slider is written out below it instead.
+        if (enabled && !tip.empty() && ImGui::IsItemHovered())
+            m_imgui->tooltip(tip, ImGui::GetFontSize() * 20.f);
+    };
+
+    row("##adj_brightness", _L("Brightness"), &m_adjust.brightness, -1.f, 1.f, "%.2f", true, {});
+    row("##adj_contrast", _L("Contrast"), &m_adjust.contrast, -1.f, 1.f, "%.2f", true, {});
+    row("##adj_sharpness", _L("Sharpness"), &m_adjust.sharpness, 0.f, 1.f, "%.2f", true,
+        _u8L("Brings out the finest detail in the image. Applied after Blur, so the two can be used "
+             "together: blur away the speckle, then sharpen the edges that remain."));
+    row("##adj_blur", _L("Blur"), &m_adjust.blur, 0.f, 1.f, "%.2f", true,
+        _u8L("Blurs the image itself. The layer's own Smoothing slider softens the relief without altering "
+             "the image, and is the one to reach for first."));
+    // Grey has no hue to turn, and the shipped library is grayscale - so on most textures this is a
+    // slider that would visibly do nothing. Disabled with the reason given, rather than hidden.
+    const bool has_color = m_adjust_source.has_color();
+    row("##adj_hue", _L("Hue"), &m_adjust.hue_deg, -180.f, 180.f, "%.0f°", has_color, {});
+    if (!has_color) {
+        ImGui::PushTextWrapPos(ImGui::GetCursorPosX() + img_w);
+        ImGui::TextDisabled("%s", _u8L("This texture is grayscale, so it has no hue to shift.").c_str());
+        ImGui::PopTextWrapPos();
+    }
+
+    if (m_imgui->button(_L("Reset")))
+        m_adjust = TextureAdjustments{};
+
+    // Hand the sliders to the layer, which is what puts the adjusted image in front of the displacement:
+    // decode_height_texture() applies preview_adjust, so the relief, the colour and the thumbnails all
+    // follow from here. Written every frame rather than only on a change, so an undo snapshot or a
+    // reselection that resets the layer cannot leave the model showing an adjustment the panel has moved
+    // on from.
+    layer->preview_adjust = m_adjust;
+    if (m_adjust != m_adjust_applied) {
+        m_adjust_applied = m_adjust;
+        invalidate_adjust_textures();
+        // Marked dirty rather than rebuilt here: the panel's own flag is consumed by the main panel's
+        // "rebuild once the mouse is released" rule, so dragging a slider recomputes the displacement
+        // once, on release, instead of on every frame of the drag. That is what keeps the UI responsive
+        // while a full-size resample and a mesh displacement happen behind it.
+        m_preview_params_dirty = true;
+        // This window is drawn after the block that consumes that flag, so the rebuild happens on a later
+        // frame - which means there has to *be* one. Cheap insurance: a slider release that generated no
+        // further canvas event would otherwise leave the flag set and the model unchanged until something
+        // unrelated redrew.
+        m_parent.set_as_dirty();
+    }
+
+    ImGui::Separator();
+    m_imgui->text_wrapped(_u8L("The model updates when you release a slider. Save as copy writes the "
+                               "adjusted image to your texture library and points this layer at it."), img_w);
+
+    const bool cancel = m_imgui->button(_L("Cancel"));
+    ImGui::SameLine();
+    // Nothing to save until a slider has actually moved.
+    m_imgui->disabled_begin(m_adjust.identity());
+    const bool as_copy = m_imgui->button(_L("Save as copy"));
+    m_imgui->disabled_end();
+
+    ImGui::End();
+
+    if (cancel || !keep_open)
+        close_image_adjust();
+    else if (as_copy)
+        commit_image_adjust(*layer);
+}
 
 void GLGizmoTextureDisplacement::remove_texture_layer(int slot)
 {
@@ -6404,7 +6761,7 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
                 ImGui::SameLine();
 
                 const std::string not_painted = _u8L("not painted");
-                const float right_w = (painted ? 0.f : ImGui::CalcTextSize(not_painted.c_str()).x + gap_s) + 3.f * frame_h + 2.f * gap_s;
+                const float right_w = (painted ? 0.f : ImGui::CalcTextSize(not_painted.c_str()).x + gap_s) + 4.f * frame_h + 3.f * gap_s;
                 const float name_w  = std::max(frame_h, ImGui::GetWindowContentRegionMax().x - card_pad - ImGui::GetCursorPosX() - gap_s - right_w);
                 ImGui::PushStyleColor(ImGuiCol_HeaderHovered, ImVec4(orca.x, orca.y, orca.z, 0.2f));
                 ImGui::PushStyleColor(ImGuiCol_HeaderActive, ImVec4(orca.x, orca.y, orca.z, 0.35f));
@@ -6418,6 +6775,16 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
                     ImGui::SameLine();
                     ImGui::TextDisabled("%s", not_painted.c_str());
                 }
+                // Between the name and the order arrows: it acts on the image the name refers to, so it
+                // belongs with the name rather than with the controls that reorder the stack.
+                ImGui::SameLine();
+                m_imgui->disabled_begin(busy || layer.empty());
+                if (icon_button(613 + layer.slot, "cog.svg", frame_h, _L("Adjust image"),
+                                _u8L("Brightness, contrast, sharpness, blur and hue, shown on the image and on the "
+                                     "model as you set them. Save as copy writes the result to your texture library "
+                                     "and points this layer at it.")))
+                    open_image_adjust(layer);
+                m_imgui->disabled_end();
                 ImGui::SameLine();
                 m_imgui->disabled_begin(busy || li == 0);
                 if (icon_button(611, "texture_displacement_move_up.svg", frame_h, _L("Move up"), _L("Move up - applied earlier"))) {
@@ -7217,10 +7584,15 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
         set_active_layer(m_picker_slot);
 
     // In this window's scope, where the popup's open request and the popup itself share one ID stack.
+    ImVec2 panel_rect_min, panel_rect_max;
     {
         const ImVec2 win_min = ImGui::GetWindowPos();
         const ImVec2 win_sz  = ImGui::GetWindowSize();
         render_texture_library_popup(win_min, ImVec2(win_min.x + win_sz.x, win_min.y + win_sz.y));
+        // Only recorded here. The image-adjustment panel is a top-level window rather than a popup, so it
+        // cannot be begun inside this one; it is drawn after GizmoImguiEnd() below.
+        panel_rect_min = win_min;
+        panel_rect_max = ImVec2(win_min.x + win_sz.x, win_min.y + win_sz.y);
     }
 
     // ImGui sliders report "changed" continuously on every frame while being dragged, not just once on
@@ -7457,6 +7829,11 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
         m_parent.request_extra_frame();
     }
     GizmoImguiEnd();
+
+    // Outside the gizmo's window, because it is a window of its own: a floating, non-modal panel that
+    // leaves the 3D view live so the relief can be watched while the sliders move. No-op when closed.
+    render_image_adjust_window(panel_rect_min, panel_rect_max);
+
     ImGuiWrapper::pop_toolbar_style();
 
     // Drawn last, over everything, via the foreground draw list: the +/- add-remove sign next to the 3D

src/slic3r/GUI/Gizmos/GLGizmoTextureDisplacement.hpp

@@ -23,6 +23,7 @@
 #include "libslic3r/Point.hpp"
 #include <imgui.h>
 #include <map>
+#include <future>
 #include <memory>
 #include <optional>
 #include "slic3r/GUI/Gizmos/GLGizmoBase.hpp"
@@ -405,6 +406,71 @@ private:
     // Panel state only, not saved with the project.
     std::array<bool, TEXTURE_DISPLACEMENT_MAX_LAYERS> m_layer_expanded{};
 
+    // ---- The image-adjustment panel ----
+    //
+    // Brightness/contrast/sharpness/blur/hue over one layer's image, shown on the image itself and
+    // updating as the sliders move. What it produces is not a set of layer parameters: it replaces the
+    // layer's *image*, so the adjusted pixels feed the colour and the displacement together and a
+    // brightness change moves the relief too (see TextureAdjustments).
+    //
+    // An ordinary floating window rather than a popup, and deliberately so. A popup dims the canvas
+    // behind it and closes on any click outside itself, which between them make it impossible to watch the
+    // relief change on the model - which is the whole point of adjusting the image here rather than in an
+    // image editor. A window leaves the 3D view live, clickable and orbitable while the panel is open.
+    void render_image_adjust_window(const ImVec2 &panel_min, const ImVec2 &panel_max);
+    // Opens the panel for `layer`, decoding its image into m_adjust_source. Sliders never re-decode
+    // the PNG.
+    void open_image_adjust(const TextureDisplacementLayer &layer);
+    // Reads `layer`'s stored image into the panel's source buffers and records which image it came from.
+    // Called when the panel opens and again whenever the layer's image is swapped under it, which is why
+    // it leaves the slider values alone. False when the image cannot be decoded.
+    bool load_image_adjust_source(const TextureDisplacementLayer &layer);
+    // Resolves the panel: writes the adjusted image into the user's texture library as a new file and
+    // points `layer` at it, which is the only way an adjustment becomes permanent. Closes the panel.
+    void commit_image_adjust(TextureDisplacementLayer &layer);
+    // Closes the panel and reverts the layer's live preview_adjust to identity, so every exit that is not
+    // a commit - Cancel, the window's close button, the gizmo closing - leaves the layer as it was found.
+    void close_image_adjust();
+    // Collects a finished preview and starts one for the current slider values. One at a time, so a drag
+    // coalesces into "whatever the sliders last said" instead of a queue of superseded frames.
+    void update_image_adjust_preview();
+
+    int                m_adjust_slot = -1; // the layer the panel is open for; -1 when closed
+    TextureAdjustments m_adjust;           // what the sliders currently say
+    // What the layer's live preview_adjust was last set from, so a slider move can be told from a frame in
+    // which nothing happened and only the former asks the displacement to be recomputed.
+    TextureAdjustments m_adjust_applied;
+
+    // The layer's image as it was when the panel opened, and a small copy of it. The sliders are applied
+    // to the small copy for the live preview and to the full-size one exactly once, on commit. Measured on
+    // a 1024x1024 with every knob engaged, a full-size pass costs 13-19 ms grayscale and 40-60 ms in
+    // colour (130-190 ms at 2048 in colour) - far too much to repeat per slider frame. The same pass on a
+    // 384 px copy is 3-4 ms / 9-12 ms, and that is all the preview box can show anyway.
+    DecodedHeightTexture m_adjust_source;
+    DecodedHeightTexture m_adjust_preview_source;
+    // Which image_data the two buffers above were decoded from, so the panel can notice the layer's image
+    // being swapped from the texture picker while it is open and re-read it. Compared, never dereferenced.
+    const void          *m_adjust_source_image = nullptr;
+    // And which volume the panel was opened on. Slot numbers are per volume, so without this a change of
+    // selection would silently rebind the open panel to whichever layer happens to hold the same slot on
+    // the newly selected object - a different image, under a panel the user opened for this one.
+    size_t               m_adjust_volume_id = 0;
+    // The preview image on screen, re-uploaded whenever a background pass finishes.
+    std::unique_ptr<GLTexture> m_adjust_preview_tex;
+
+    // The live preview runs on its own thread rather than on the UI thread or on the plater's job
+    // worker. Not the UI thread because even the small pass is milliseconds and this runs while a slider
+    // is being dragged; not the job worker because that is a single FIFO shared with Bake and the
+    // displacement preview (see queue_preview_job()), where a per-frame image filter would sit behind -
+    // and delay - multi-second mesh work.
+    std::future<DecodedHeightTexture> m_adjust_preview_job;
+    TextureAdjustments                m_adjust_preview_running; // what the in-flight pass is computing
+    TextureAdjustments                m_adjust_preview_shown;   // what m_adjust_preview_tex holds
+    bool                              m_adjust_preview_valid = false;
+    // Drops the GPU copies of the layer's image so the next frame rebuilds them from the decode, which
+    // is where the live adjustment is applied. Called whenever the panel moves or reverts it.
+    void invalidate_adjust_textures();
+
     // "Adjust Texture" mode: instead of painting, dragging an on-canvas handle changes the active
     // layer's offset. The handle is a flat panel lying in the paint patch's own tangent plane
     // (a "pan" - drag anywhere on it for free 2D movement), plus two arrows along the patch's
@@ -423,8 +489,8 @@ private:
     // obvious whether the next stroke adds paint (default) or erases it (Shift). Uses ImGui's
     // foreground draw list, so it must be called from inside the gizmo's ImGui frame.
     void render_paint_cursor_hint();
-    // Mesh-local tangent-plane basis at m_adjust_anchor_normal: box_projection_axes(), so dragging
-    // on-canvas maps consistently onto offset whichever face the anchor is on.
+    // Mesh-local tangent-plane basis at m_adjust_anchor_normal, matching project_planar()'s
+    // dominant-axis convention so dragging on-canvas maps consistently onto offset.
     void adjust_tangent_basis(Vec3f &u_axis, Vec3f &v_axis) const;
 
     // The plane a drag is measured against: the paint patch's anchor, lifted clear of the surface.
@@ -878,6 +944,7 @@ private:
     enum class UVBackground { None, Height, Checker };
     UVBackground m_uv_editor_bg = UVBackground::None;
     float        m_uv_editor_bg_smoothing = -1.f; // smoothing the height backdrop was uploaded at
+    TextureAdjustments m_uv_editor_bg_adjust;        // and the live image adjustment it was uploaded at
     const void  *m_uv_editor_bg_image     = nullptr; // the layer image it was uploaded from
     // Per-chart distortion heatmap colour for the UV pane (#7/#14), computed once when the unwrap is
     // re-solved (relative stretch doesn't change when islands are merely moved), fed to the canvas only

src/slic3r/GUI/TextureLibrary.cpp

@@ -27,6 +27,7 @@
 #include <wx/mstream.h>
 
 #include "libslic3r/PNGReadWrite.hpp"
+#include "libslic3r/TextureDisplacement.hpp"
 #include "libslic3r/Utils.hpp"
 
 #include "libslic3r/AppConfig.hpp"
@@ -158,6 +159,28 @@ bool encode_png_bytes(const wxImage &image, std::vector<unsigned char> &out, std
                                   : encode_gray_png_bytes(image, out, error);
 }
 
+// A wxImage over decoded pixels, so the encoders above can be reached from an in-memory image as well as
+// from a file. Grayscale is expanded to the three equal channels wxImage always stores, which is what
+// image_has_color() then reads as "no colour" - so a grey image still encodes as a grayscale PNG.
+//
+// `scratch` holds the pixel buffer: the wxImage is constructed over it without taking ownership, so it
+// has to outlive every use of the returned image.
+wxImage image_from_decoded(const DecodedHeightTexture &image, std::vector<unsigned char> &scratch)
+{
+    if (image.empty())
+        return wxImage();
+
+    const size_t n = size_t(image.width) * size_t(image.height);
+    scratch.resize(n * 3);
+    if (image.has_color())
+        scratch.assign(image.rgb.begin(), image.rgb.end());
+    else
+        for (size_t i = 0; i < n; ++i)
+            scratch[i * 3] = scratch[i * 3 + 1] = scratch[i * 3 + 2] = image.pixels[i];
+
+    return wxImage(image.width, image.height, scratch.data(), /* static_data */ true);
+}
+
 std::vector<unsigned char> read_file_bytes(const std::string &path)
 {
     std::ifstream ifs(path, std::ios::binary);
@@ -186,6 +209,42 @@ bool is_supported_height_map(const std::vector<unsigned char> &bytes)
 std::vector<TextureLibraryEntry> g_library;
 bool                             g_library_scanned = false;
 
+// Writes `bytes` into the user's own texture folder as `stem`.png, uniquified so an existing texture -
+// shipped-name collision, or a second edit of the same source - is never overwritten. Returns the new
+// file's library entry. Shared by import_texture_to_library() and save_texture_to_library(), which
+// differ only in where their bytes came from.
+std::optional<TextureLibraryEntry> write_user_texture(const std::vector<unsigned char> &bytes, const std::string &stem,
+                                                      std::string &error)
+{
+    const std::string user_dir = user_texture_dir();
+    if (user_dir.empty()) {
+        error = _u8L("Could not create the folder for imported textures.");
+        return std::nullopt;
+    }
+
+    boost::filesystem::path dest = boost::filesystem::path(user_dir) / (stem + ".png");
+    for (int i = 2; boost::filesystem::exists(dest); ++i)
+        dest = boost::filesystem::path(user_dir) / (stem + " (" + std::to_string(i) + ").png");
+
+    {
+        boost::nowide::ofstream ofs(dest.string(), std::ios::binary);
+        ofs.write(reinterpret_cast<const char *>(bytes.data()), std::streamsize(bytes.size()));
+        if (!ofs.good()) {
+            error = _u8L("Failed to save the imported texture.");
+            return std::nullopt;
+        }
+    }
+
+    texture_library(true); // pick the new file up
+    const std::string dest_str = dest.string();
+    for (const TextureLibraryEntry &e : g_library)
+        if (e.path == dest_str)
+            return e;
+
+    error = _u8L("Failed to save the imported texture.");
+    return std::nullopt;
+}
+
 // The user's own textures, most recently used first, kept in the app config. File names are stored rather
 // than paths so the order survives a moved data directory; '/' separates them because no platform allows
 // it inside a file name. Bounded so a long-lived config does not grow a line without end.
@@ -317,12 +376,6 @@ bool remove_user_texture(const std::string &path, std::string &error)
 
 std::optional<TextureLibraryEntry> import_texture_to_library(const std::string &source_path, std::string &error)
 {
-    const std::string user_dir = user_texture_dir();
-    if (user_dir.empty()) {
-        error = _u8L("Could not create the folder for imported textures.");
-        return std::nullopt;
-    }
-
     wxImage image;
     if (!image.LoadFile(from_u8(source_path)) || !image.IsOk()) {
         error = _u8L("Could not load the selected image.");
@@ -333,30 +386,7 @@ std::optional<TextureLibraryEntry> import_texture_to_library(const std::string &
     if (!encode_png_bytes(image, bytes, error))
         return std::nullopt;
 
-    // Never overwrite an existing texture (the user's or, if they picked the same name twice, their
-    // own earlier import) - uniquify instead.
-    const std::string       stem = boost::filesystem::path(source_path).stem().string();
-    boost::filesystem::path dest = boost::filesystem::path(user_dir) / (stem + ".png");
-    for (int i = 2; boost::filesystem::exists(dest); ++i)
-        dest = boost::filesystem::path(user_dir) / (stem + " (" + std::to_string(i) + ").png");
-
-    {
-        boost::nowide::ofstream ofs(dest.string(), std::ios::binary);
-        ofs.write(reinterpret_cast<const char *>(bytes.data()), std::streamsize(bytes.size()));
-        if (!ofs.good()) {
-            error = _u8L("Failed to save the imported texture.");
-            return std::nullopt;
-        }
-    }
-
-    texture_library(true); // pick the new file up
-    const std::string dest_str = dest.string();
-    for (const TextureLibraryEntry &e : g_library)
-        if (e.path == dest_str)
-            return e;
-
-    error = _u8L("Failed to save the imported texture.");
-    return std::nullopt;
+    return write_user_texture(bytes, boost::filesystem::path(source_path).stem().string(), error);
 }
 
 std::shared_ptr<std::vector<unsigned char>> load_texture_image_data(const std::string &path, std::string &error)
@@ -382,4 +412,21 @@ std::shared_ptr<std::vector<unsigned char>> load_texture_image_data(const std::s
     return std::make_shared<std::vector<unsigned char>>(std::move(converted));
 }
 
+std::optional<TextureLibraryEntry> save_texture_to_library(const DecodedHeightTexture &image, const std::string &stem,
+                                                           std::string &error)
+{
+    std::vector<unsigned char> scratch;
+    const wxImage              wx = image_from_decoded(image, scratch);
+    if (!wx.IsOk()) {
+        error = _u8L("The selected image is empty.");
+        return std::nullopt;
+    }
+
+    std::vector<unsigned char> bytes;
+    if (!encode_png_bytes(wx, bytes, error))
+        return std::nullopt;
+
+    return write_user_texture(bytes, stem.empty() ? std::string("texture") : stem, error);
+}
+
 } // namespace Slic3r::GUI

src/slic3r/GUI/TextureLibrary.hpp

@@ -6,6 +6,8 @@
 #include <string>
 #include <vector>
 
+#include "libslic3r/TextureDisplacement.hpp"
+
 namespace Slic3r::GUI {
 
 // One selectable height-map texture in the texture-displacement gizmo's texture picker.
@@ -57,6 +59,14 @@ std::optional<TextureLibraryEntry> import_texture_to_library(const std::string &
 // Returns nullptr with `error` set if the file cannot be read or decoded at all.
 std::shared_ptr<std::vector<unsigned char>> load_texture_image_data(const std::string &path, std::string &error);
 
+// Writes `image` into user_texture_dir() as a new PNG named after `stem` (uniquified if taken, so an
+// existing texture is never overwritten) and returns its library entry. The in-memory counterpart of
+// import_texture_to_library(), for an image that was edited rather than read off disk.
+//
+// Returns nullopt with `error` set on failure.
+std::optional<TextureLibraryEntry> save_texture_to_library(const DecodedHeightTexture &image, const std::string &stem,
+                                                           std::string &error);
+
 } // namespace Slic3r::GUI
 
 #endif // slic3r_TextureLibrary_hpp_

tests/libslic3r/test_texture_displacement.cpp

@@ -28,6 +28,7 @@
 
 #include <algorithm>
 #include <array>
+#include <functional>
 #include <cmath>
 #include <fstream>
 #include <limits>
@@ -1300,6 +1301,294 @@ TEST_CASE("TextureDisplacement: the step cutter only cuts inside the region", "[
     }
 }
 
+// ---- Image adjustments (the gizmo's image-adjustment panel) ----------------------------------------
+
+// A grayscale ramp 0..255 across the width, so every input level is present exactly once per row and a
+// tonal curve can be read straight off the output.
+static DecodedHeightTexture make_gray_ramp(int w = 256, int h = 4)
+{
+    DecodedHeightTexture t;
+    t.width  = w;
+    t.height = h;
+    t.pixels.resize(size_t(w) * size_t(h));
+    for (int y = 0; y < h; ++y)
+        for (int x = 0; x < w; ++x)
+            t.pixels[size_t(y) * size_t(w) + size_t(x)] = uint8_t(x * 255 / std::max(1, w - 1));
+    return t;
+}
+
+// A one-texel checkerboard of 0 and 255 - the highest spatial frequency the grid can hold, which is what
+// a blur has to remove and a downscale has to average rather than drop.
+static DecodedHeightTexture make_gray_checkerboard(int w = 16, int h = 16)
+{
+    DecodedHeightTexture t;
+    t.width  = w;
+    t.height = h;
+    t.pixels.resize(size_t(w) * size_t(h));
+    for (int y = 0; y < h; ++y)
+        for (int x = 0; x < w; ++x)
+            t.pixels[size_t(y) * size_t(w) + size_t(x)] = ((x + y) % 2 == 0) ? 0 : 255;
+    return t;
+}
+
+static DecodedHeightTexture make_rgb_flat(uint8_t r, uint8_t g, uint8_t b, int w = 8, int h = 8)
+{
+    DecodedHeightTexture t;
+    t.width  = w;
+    t.height = h;
+    t.pixels.resize(size_t(w) * size_t(h));
+    t.rgb.resize(size_t(w) * size_t(h) * 3);
+    for (size_t i = 0; i < size_t(w) * size_t(h); ++i) {
+        t.rgb[i * 3]     = r;
+        t.rgb[i * 3 + 1] = g;
+        t.rgb[i * 3 + 2] = b;
+        t.pixels[i]      = uint8_t(std::lround(0.299 * r + 0.587 * g + 0.114 * b));
+    }
+    return t;
+}
+
+TEST_CASE("an adjustment that moves no slider returns the image unchanged", "[TextureDisplacement]")
+{
+    const DecodedHeightTexture src = make_gray_ramp();
+    const DecodedHeightTexture out = apply_texture_adjustments(src, TextureAdjustments{});
+    CHECK(out.width == src.width);
+    CHECK(out.height == src.height);
+    CHECK(out.pixels == src.pixels);
+    CHECK(TextureAdjustments{}.identity());
+}
+
+TEST_CASE("brightness reaches pure white and pure black only at the ends of its range", "[TextureDisplacement]")
+{
+    const DecodedHeightTexture src = make_gray_ramp();
+
+    TextureAdjustments up;
+    up.brightness = 1.f;
+    const DecodedHeightTexture white = apply_texture_adjustments(src, up);
+    CHECK(std::all_of(white.pixels.begin(), white.pixels.end(), [](uint8_t v) { return v == 255; }));
+
+    TextureAdjustments down;
+    down.brightness = -1.f;
+    const DecodedHeightTexture black = apply_texture_adjustments(src, down);
+    CHECK(std::all_of(black.pixels.begin(), black.pixels.end(), [](uint8_t v) { return v == 0; }));
+}
+
+TEST_CASE("brightness lifts the image without flattening it into a clipped plateau", "[TextureDisplacement]")
+{
+    // The reason brightness is a lift toward white rather than an additive offset: an offset would drive
+    // everything above mid-grey to a flat 255, and since this image is also the height map that region
+    // would bake as flat relief. Half a stop up must leave almost nothing at pure white.
+    const DecodedHeightTexture src = make_gray_ramp();
+    TextureAdjustments         adj;
+    adj.brightness = 0.5f;
+    const DecodedHeightTexture out = apply_texture_adjustments(src, adj);
+
+    REQUIRE(out.pixels.size() == src.pixels.size());
+    const size_t clipped = size_t(std::count(out.pixels.begin(), out.pixels.end(), uint8_t(255)));
+    CHECK(clipped * 100 < out.pixels.size()); // under 1%; an additive shift would clip half the ramp
+
+    // Every texel got brighter, and the curve stays ordered: brighter in means brighter out.
+    for (size_t i = 0; i < out.pixels.size(); ++i)
+        REQUIRE(out.pixels[i] >= src.pixels[i]);
+    for (int x = 1; x < out.width; ++x)
+        REQUIRE(out.pixels[size_t(x)] >= out.pixels[size_t(x - 1)]);
+}
+
+TEST_CASE("contrast at its lowest flattens the image to mid-grey and at its highest spreads it apart",
+          "[TextureDisplacement]")
+{
+    const DecodedHeightTexture src = make_gray_ramp();
+
+    TextureAdjustments flat;
+    flat.contrast = -1.f;
+    const DecodedHeightTexture grey = apply_texture_adjustments(src, flat);
+    // One value everywhere - the pivot. Which exact level that rounds to is not the point.
+    CHECK(std::adjacent_find(grey.pixels.begin(), grey.pixels.end(), std::not_equal_to<uint8_t>()) ==
+          grey.pixels.end());
+
+    TextureAdjustments hard;
+    hard.contrast = 1.f;
+    const DecodedHeightTexture split = apply_texture_adjustments(src, hard);
+    // A threshold about the pivot: the dark end of the ramp goes to black, the light end to white.
+    CHECK(split.pixels[0] == 0);
+    CHECK(split.pixels[size_t(split.width - 1)] == 255);
+}
+
+TEST_CASE("blur removes the finest detail and sharpness exaggerates an edge", "[TextureDisplacement]")
+{
+    // Blur: a one-texel checkerboard is the highest frequency the grid holds, so a blur has to collapse it
+    // toward its own mean. Measured as mean absolute deviation, which needs no assumption about the mean.
+    const DecodedHeightTexture checker = make_gray_checkerboard(32, 32);
+    const auto                 deviation = [](const DecodedHeightTexture &t) {
+        double mean = 0.;
+        for (uint8_t v : t.pixels)
+            mean += double(v);
+        mean /= double(t.pixels.size());
+        double dev = 0.;
+        for (uint8_t v : t.pixels)
+            dev += std::abs(double(v) - mean);
+        return dev / double(t.pixels.size());
+    };
+    TextureAdjustments blur;
+    blur.blur = 1.f;
+    CHECK(deviation(apply_texture_adjustments(checker, blur)) < 0.25 * deviation(checker));
+
+    // Sharpness: an unsharp mask pushes each side of a step further from the other, so the step
+    // overshoots - darker than the dark side just inside it, brighter than the bright side just inside.
+    DecodedHeightTexture step;
+    step.width  = 64;
+    step.height = 8;
+    step.pixels.assign(size_t(step.width) * size_t(step.height), 100);
+    for (int y = 0; y < step.height; ++y)
+        for (int x = step.width / 2; x < step.width; ++x)
+            step.pixels[size_t(y) * size_t(step.width) + size_t(x)] = 150;
+
+    TextureAdjustments sharp;
+    sharp.sharpness = 1.f;
+    const DecodedHeightTexture sharpened = apply_texture_adjustments(step, sharp);
+    const size_t               row       = size_t(step.height / 2) * size_t(step.width);
+    const size_t               mid       = size_t(step.width / 2);
+    CHECK(sharpened.pixels[row + mid - 1] < 100); // undershoot on the dark side of the step
+    CHECK(sharpened.pixels[row + mid] > 150);     // overshoot on the light side
+}
+
+TEST_CASE("a grayscale image stays grayscale and its hue slider does nothing", "[TextureDisplacement]")
+{
+    const DecodedHeightTexture src = make_gray_ramp();
+    REQUIRE_FALSE(src.has_color());
+
+    TextureAdjustments hue;
+    hue.hue_deg = 120.f;
+    const DecodedHeightTexture out = apply_texture_adjustments(src, hue);
+    // Not promoted to RGB: a grey image has no colour to offer the layer's colour feature, and storing it
+    // as RGB would triple the PNG for a row of identical greys.
+    CHECK_FALSE(out.has_color());
+    CHECK(out.rgb.empty());
+    CHECK(out.pixels == src.pixels);
+}
+
+TEST_CASE("a colour image's height stays the luminance of its adjusted colour", "[TextureDisplacement]")
+{
+    // The invariant that keeps the relief and the colour from drifting apart: whatever the adjustment did
+    // to the channels, the height is recomputed from the channels that came out.
+    const DecodedHeightTexture src = make_rgb_flat(200, 60, 30);
+    REQUIRE(src.has_color());
+
+    TextureAdjustments adj;
+    adj.brightness = 0.2f;
+    adj.contrast   = 0.3f;
+    adj.hue_deg    = 75.f;
+    const DecodedHeightTexture out = apply_texture_adjustments(src, adj);
+    REQUIRE(out.has_color());
+
+    for (size_t i = 0; i < out.pixels.size(); ++i) {
+        const long expect = std::lround(0.299 * out.rgb[i * 3] + 0.587 * out.rgb[i * 3 + 1] +
+                                        0.114 * out.rgb[i * 3 + 2]);
+        REQUIRE(long(out.pixels[i]) == expect);
+    }
+    // The hue turn actually moved the colour, so the check above is not passing on an unchanged image.
+    CHECK(out.rgb != src.rgb);
+}
+
+TEST_CASE("a full turn of the hue leaves a colour where it started", "[TextureDisplacement]")
+{
+    const DecodedHeightTexture src = make_rgb_flat(200, 60, 30);
+    TextureAdjustments         adj;
+    adj.hue_deg                    = 360.f;
+    const DecodedHeightTexture out = apply_texture_adjustments(src, adj);
+    REQUIRE(out.has_color());
+    // Rounding through 8-bit channels, so a level or two of slack rather than exact equality.
+    for (size_t i = 0; i < out.rgb.size(); ++i)
+        REQUIRE(std::abs(int(out.rgb[i]) - int(src.rgb[i])) <= 2);
+}
+
+TEST_CASE("the adjustment blur radius ramps from zero and stays under its cost cap", "[TextureDisplacement]")
+{
+    CHECK_THAT(adjustment_blur_radius(0.f, 512, 512), Catch::Matchers::WithinAbs(0.f, 1e-6f));
+    // 5% of the short side, as the Smoothing slider uses.
+    CHECK_THAT(adjustment_blur_radius(1.f, 512, 512), Catch::Matchers::WithinAbs(25.6f, 1e-3f));
+    CHECK_THAT(adjustment_blur_radius(0.5f, 512, 512), Catch::Matchers::WithinAbs(12.8f, 1e-3f));
+    // Capped, so a large image at the top of the slider cannot cost without bound.
+    CHECK_THAT(adjustment_blur_radius(1.f, 8192, 8192), Catch::Matchers::WithinAbs(48.f, 1e-3f));
+    // Sized off the short side, not the long one.
+    CHECK_THAT(adjustment_blur_radius(1.f, 4096, 200), Catch::Matchers::WithinAbs(10.f, 1e-3f));
+}
+
+TEST_CASE("downscaling a height texture averages the texels it drops and never upscales",
+          "[TextureDisplacement]")
+{
+    // Averaging, not decimation: a one-texel checkerboard halved must come out uniformly mid-grey. Picking
+    // one texel per block would instead come out all black or all white - detail the adjustment never
+    // produced, shown in the preview.
+    const DecodedHeightTexture small = downscale_height_texture(make_gray_checkerboard(16, 16), 8);
+    CHECK(small.width == 8);
+    CHECK(small.height == 8);
+    CHECK(std::all_of(small.pixels.begin(), small.pixels.end(), [](uint8_t v) { return v == 127; }));
+
+    // Already within the limit: handed back as it is.
+    const DecodedHeightTexture ramp = make_gray_ramp(64, 4);
+    const DecodedHeightTexture same = downscale_height_texture(ramp, 256);
+    CHECK(same.width == ramp.width);
+    CHECK(same.height == ramp.height);
+    CHECK(same.pixels == ramp.pixels);
+
+    // Aspect preserved, and a colour source keeps its colour.
+    const DecodedHeightTexture wide = downscale_height_texture(make_rgb_flat(200, 60, 30, 400, 100), 100);
+    CHECK(wide.width == 100);
+    CHECK(wide.height == 25);
+    CHECK(wide.has_color());
+}
+
+TEST_CASE("a layer's live image adjustment reaches its decode", "[TextureDisplacement]")
+{
+    // This is what makes the image-adjustment panel's sliders move the relief: decode_height_texture()
+    // applies the layer's preview_adjust, so everything downstream of the decode - the displacement, the
+    // colour, the thumbnails, the bake - sees the adjusted image without being told about the panel.
+    TextureDisplacementLayer layer;
+    layer.image_data = make_checkerboard_png(32, 32);
+
+    const DecodedHeightTexture raw = decode_height_texture(layer);
+    REQUIRE_FALSE(raw.empty());
+
+    // An untouched panel, and a closed one, cost nothing and change nothing.
+    layer.preview_adjust = TextureAdjustments{};
+    CHECK(decode_height_texture(layer).pixels == raw.pixels);
+
+    layer.preview_adjust.brightness = 0.5f;
+    const DecodedHeightTexture bright = decode_height_texture(layer);
+    CHECK(bright.pixels != raw.pixels);
+    CHECK(bright.pixels == apply_texture_adjustments(raw, layer.preview_adjust).pixels);
+
+    // Back to identity gives the stored image back, so closing the panel really does revert the layer.
+    layer.preview_adjust = TextureAdjustments{};
+    CHECK(decode_height_texture(layer).pixels == raw.pixels);
+}
+
+TEST_CASE("changing a live adjustment is not served the previous one from cache", "[TextureDisplacement]")
+{
+    // The decode caches by the image_data pointer, which does not change while a slider moves - so the
+    // adjustment has to be part of the key or every slider move past the first would redraw the same
+    // pixels. Same for the smoothed copy, which is computed on top of the adjusted one.
+    TextureDisplacementLayer layer;
+    layer.image_data = make_checkerboard_png(32, 32);
+    const DecodedHeightTexture raw = decode_height_texture(layer);
+    REQUIRE_FALSE(raw.empty());
+
+    layer.preview_adjust.brightness = 0.5f;
+    const std::vector<uint8_t> bright = decode_height_texture(layer).pixels;
+    layer.preview_adjust.brightness   = -0.5f;
+    const std::vector<uint8_t> dark   = decode_height_texture(layer).pixels;
+    CHECK(bright != dark);
+    CHECK(dark == apply_texture_adjustments(raw, layer.preview_adjust).pixels);
+
+    // The same question again with smoothing on, which is cached separately and keyed by both.
+    layer.smoothing                 = 0.5f;
+    layer.preview_adjust.brightness = 0.5f;
+    const std::vector<uint8_t> smooth_bright = decode_height_texture(layer).pixels;
+    layer.preview_adjust.brightness          = -0.5f;
+    const std::vector<uint8_t> smooth_dark   = decode_height_texture(layer).pixels;
+    CHECK(smooth_bright != smooth_dark);
+}
+
 // ---------------------------------------------------------------------------------------------
 // Texture smoothing
 // ---------------------------------------------------------------------------------------------
@@ -1652,321 +1941,6 @@ TEST_CASE("Per-corner LSCM UVs give each triangle its own island's placement", "
     CHECK(differs);
 }
 
-// ---------------------------------------------------------------------------------------------
-// UV orientation: which way up a texture lands on the model.
-//
-// v = 0 is the height map's *first* pixel row, i.e. its top (DecodedHeightTexture::sample(), and
-// the UV editor negates Y on screen for the same reason). So "the image is the right way up" is the
-// statement that the row a point samples gets *lower* as the point moves up the face, and "it is
-// not left-right mirrored" is that the column gets higher as the point moves to the right of a
-// viewer standing outside the model. Both are measured below by sampling a ramp whose value says
-// which row (or column) it came from, which settles the question without having to reason about the
-// uv transform at all.
-
-static constexpr int   RAMP_N      = 64;   // the ramp texture's size, in texels
-static constexpr float RAMP_TILING = 40.f; // mm per tile
-static constexpr float CUBE_HALF   = 5.f;  // half extent of the cube the probes walk over
-// How far a probe steps off a face centre. Short on purpose: the cylindrical and spherical u is an
-// arc length (angle * radius), so a long step also changes the radius, and that term swamps the
-// angular one. It is symmetric about the face centre, so at a short step it cancels between the two
-// readings a check compares.
-static constexpr float RAMP_STEP   = 1.f;
-// What one step's worth of travel is in ramp rows: 2 * RAMP_STEP mm of separation, RAMP_N texels per
-// RAMP_TILING mm. Halved as the margin a check demands, so "flat" cannot pass as either direction.
-static constexpr double RAMP_MARGIN = RAMP_N * RAMP_STEP / RAMP_TILING;
-
-// A height map whose rows (or columns) carry a linear ramp: row r holds 3 + 4r, so the sampled
-// height identifies the row. Built directly rather than through a PNG because these tests are about
-// the projection, not the decoder - decode_height_texture() has its own tests.
-static DecodedHeightTexture ramp_texture(bool by_row)
-{
-    DecodedHeightTexture t;
-    t.width = t.height = RAMP_N;
-    t.pixels.resize(size_t(RAMP_N) * size_t(RAMP_N));
-    for (int y = 0; y < RAMP_N; ++y)
-        for (int x = 0; x < RAMP_N; ++x)
-            t.pixels[size_t(y) * size_t(RAMP_N) + size_t(x)] = uint8_t(3 + 4 * (by_row ? y : x));
-    return t;
-}
-
-// uv 0.5 at the cube's centre, and a tile wide enough that every point the probes visit stays well
-// inside the one tile - so no reading is a wrapped-around neighbour of the one it is compared with.
-static TextureDisplacementLayer ramp_layer(TextureProjectionMethod method)
-{
-    TextureDisplacementLayer layer;
-    layer.projection_method = method;
-    layer.tiling_scale      = RAMP_TILING;
-    layer.offset            = Vec2f(0.5f, 0.5f);
-    layer.depth_mm          = 1.f;
-    return layer;
-}
-
-// Which row (or column) of `ramp` the layer reads at `p`. Fractional, because a point between two
-// texels reads the ramp between them; only the direction it moves in matters here.
-static double ramp_index(const DecodedHeightTexture &ramp, const TextureDisplacementLayer &layer, const Vec3f &p,
-                         const Vec3f &n, const Vec3f &center = Vec3f(Vec3f::Zero()),
-                         const Vec3f &axis = Vec3f(Vec3f::UnitZ()))
-{
-    return (double(sample_layer_height(ramp, layer, p, n, center, axis, nullptr)) * 255.0 - 3.0) / 4.0;
-}
-
-// How a viewer standing outside the model sees a face: their right, and their up. Up is world +Z on
-// the four upright faces; on the top and bottom, where +Z is edge on, it is world +Y.
-static void outside_viewer_frame(const Vec3f &n, Vec3f &right, Vec3f &up)
-{
-    up    = (std::abs(n.z()) < 0.9f) ? Vec3f(0.f, 0.f, 1.f) : Vec3f(0.f, 1.f, 0.f);
-    right = Vec3f((-n).cross(up).normalized());
-}
-
-static const std::array<std::pair<const char *, Vec3f>, 6> CUBE_FACES = { {
-    { "+X", Vec3f(1.f, 0.f, 0.f) },
-    { "-X", Vec3f(-1.f, 0.f, 0.f) },
-    { "+Y", Vec3f(0.f, 1.f, 0.f) },
-    { "-Y", Vec3f(0.f, -1.f, 0.f) },
-    { "+Z", Vec3f(0.f, 0.f, 1.f) },
-    { "-Z", Vec3f(0.f, 0.f, -1.f) },
-} };
-
-TEST_CASE("the box projection lands a texture upright and unmirrored on all six faces of a cube",
-          "[TextureDisplacement]")
-{
-    const DecodedHeightTexture     rows  = ramp_texture(true);
-    const DecodedHeightTexture     cols  = ramp_texture(false);
-    const TextureDisplacementLayer layer = ramp_layer(TextureProjectionMethod::Triplanar);
-
-    for (const auto &[name, n] : CUBE_FACES) {
-        DYNAMIC_SECTION("face " << name)
-        {
-            Vec3f right, up;
-            outside_viewer_frame(n, right, up);
-            const Vec3f centre = n * CUBE_HALF;
-
-            // Upright: the row read near the top of the face is nearer the image's first row.
-            const double row_up   = ramp_index(rows, layer, centre + up * RAMP_STEP, n);
-            const double row_down = ramp_index(rows, layer, centre - up * RAMP_STEP, n);
-            INFO("row at the top of the face " << row_up << ", at the bottom " << row_down);
-            CHECK(row_down - row_up > RAMP_MARGIN);
-
-            // Unmirrored: the column read to the viewer's right is further into the image. Without a
-            // per-side sign this fails on exactly the three faces facing away - -X, +Y and -Z - which
-            // is the mirroring a bare v flip leaves behind.
-            const double col_left  = ramp_index(cols, layer, centre - right * RAMP_STEP, n);
-            const double col_right = ramp_index(cols, layer, centre + right * RAMP_STEP, n);
-            INFO("column at the left of the face " << col_left << ", at the right " << col_right);
-            CHECK(col_right - col_left > RAMP_MARGIN);
-        }
-    }
-}
-
-TEST_CASE("every projection method lands a texture upright on an upright face", "[TextureDisplacement]")
-{
-    const DecodedHeightTexture rows = ramp_texture(true);
-    // ViewProjected is one flat projection from the captured camera rather than a per-face map, so its
-    // "up" is the projector's own (view_project_up), which the default capture puts at +Y.
-    const auto method = GENERATE(TextureProjectionMethod::Triplanar, TextureProjectionMethod::Cylindrical,
-                                 TextureProjectionMethod::Spherical, TextureProjectionMethod::ViewProjected);
-    const TextureDisplacementLayer layer = ramp_layer(method);
-
-    for (const auto &[name, n] : CUBE_FACES) {
-        // Only the four upright faces: on the top and bottom a cylinder's v is constant (they are its
-        // caps) and a sphere's is at an extremum (they are its poles), so neither says anything about
-        // which way up the image is.
-        if (std::abs(n.z()) > 0.9f)
-            continue;
-        DYNAMIC_SECTION("method " << int(method) << ", face " << name)
-        {
-            const Vec3f up = (method == TextureProjectionMethod::ViewProjected) ? layer.view_project_up :
-                                                                                 Vec3f(0.f, 0.f, 1.f);
-            const Vec3f centre = n * CUBE_HALF;
-            const double row_up   = ramp_index(rows, layer, centre + up * RAMP_STEP, n);
-            const double row_down = ramp_index(rows, layer, centre - up * RAMP_STEP, n);
-            INFO("row at the top " << row_up << ", at the bottom " << row_down);
-            CHECK(row_down - row_up > RAMP_MARGIN);
-        }
-    }
-}
-
-TEST_CASE("the cylindrical and spherical wraps run left to right as seen from outside", "[TextureDisplacement]")
-{
-    const DecodedHeightTexture cols = ramp_texture(false);
-    const auto method = GENERATE(TextureProjectionMethod::Cylindrical, TextureProjectionMethod::Spherical);
-    const TextureDisplacementLayer layer = ramp_layer(method);
-
-    for (const auto &[name, n] : CUBE_FACES) {
-        // The caps and poles are out, as above - u is undefined on the axis. So is whichever face the
-        // atan2 branch cut runs through, where u jumps from +pi to -pi: that is a real seam in both
-        // projections, and a reading taken across it compares two opposite sides of the model.
-        if (std::abs(n.z()) > 0.9f)
-            continue;
-        const bool on_the_cut = (method == TextureProjectionMethod::Cylindrical) ? (n.y() < -0.9f) : (n.x() < -0.9f);
-        if (on_the_cut)
-            continue;
-        DYNAMIC_SECTION("method " << int(method) << ", face " << name)
-        {
-            Vec3f right, up;
-            outside_viewer_frame(n, right, up);
-            const Vec3f  centre    = n * CUBE_HALF;
-            const double col_left  = ramp_index(cols, layer, centre - right * RAMP_STEP, n);
-            const double col_right = ramp_index(cols, layer, centre + right * RAMP_STEP, n);
-            INFO("column at the left " << col_left << ", at the right " << col_right);
-            CHECK(col_right - col_left > RAMP_MARGIN);
-        }
-    }
-}
-
-TEST_CASE("an unwrapped cube's flat charts are laid out the right way up", "[TextureDisplacement]")
-{
-    indexed_triangle_set cube = its_make_cube(2. * CUBE_HALF, 2. * CUBE_HALF, 2. * CUBE_HALF);
-    for (Vec3f &v : cube.vertices)
-        v -= Vec3f(CUBE_HALF, CUBE_HALF, CUBE_HALF);
-
-    const PatchUnwrap unwrap = compute_patch_unwrap(cube, LSCM_DEFAULT_SEAM_ANGLE_DEG);
-    REQUIRE_FALSE(unwrap.empty());
-    REQUIRE(unwrap.chart_count == 6); // one flat chart per face, cut at the 90-degree edges
-
-    // Each chart carries one face. The four upright ones span world Z, and their v has to grow
-    // downwards like every other projection's - whatever the packing then did with the island.
-    int upright_charts = 0;
-    for (int c = 0; c < unwrap.chart_count; ++c) {
-        int top = -1, bottom = -1;
-        for (size_t i = 0; i < unwrap.uvs.size(); ++i) {
-            if (unwrap.vertex_chart[i] != c)
-                continue;
-            const float z = cube.vertices[size_t(unwrap.source_vertex[i])].z();
-            if (top < 0 || z > cube.vertices[size_t(unwrap.source_vertex[size_t(top)])].z())
-                top = int(i);
-            if (bottom < 0 || z < cube.vertices[size_t(unwrap.source_vertex[size_t(bottom)])].z())
-                bottom = int(i);
-        }
-        REQUIRE(top >= 0);
-        REQUIRE(bottom >= 0);
-        const float v_top = unwrap.uvs[size_t(top)].y(), v_bottom = unwrap.uvs[size_t(bottom)].y();
-        if (std::abs(v_top - v_bottom) < 1e-3f)
-            continue; // a cap: the whole chart is at one height, so it has no up
-        ++upright_charts;
-        DYNAMIC_SECTION("chart " << c)
-        {
-            INFO("v at the chart's topmost vertex " << v_top << ", at its bottommost " << v_bottom);
-            CHECK(v_bottom - v_top > 1.f);
-        }
-    }
-    CHECK(upright_charts == 4); // the four sides; the top and bottom faces are the caps skipped above
-}
-
-TEST_CASE("project_planar agrees with the box projection's own axes", "[TextureDisplacement]")
-{
-    // The two express the same table in different shapes - one a pair of world axes for the GUI, the
-    // other the closed form the bake's hot path uses - so they are checked against each other here
-    // rather than left to drift apart.
-    const Vec3f p(2.f, -3.f, 7.f);
-    for (const auto &[name, n] : CUBE_FACES) {
-        DYNAMIC_SECTION("face " << name)
-        {
-            Vec3f u_axis, v_axis;
-            box_projection_axes(n, u_axis, v_axis);
-            const Vec2f planar = project_planar(p, n);
-            CHECK_THAT(planar.x(), WithinAbs(p.dot(u_axis), 1e-5f));
-            CHECK_THAT(planar.y(), WithinAbs(p.dot(v_axis), 1e-5f));
-            // Right-handed for a viewer outside the model: u to their right, v down, so u x v points
-            // into the surface. Getting this wrong is exactly what mirrors a face.
-            CHECK_THAT(u_axis.cross(v_axis).dot(n), WithinAbs(-1.f, 1e-5f));
-        }
-    }
-}
-
-// An image with a different value in each quadrant, so one bake says both which way up it landed
-// and whether it came out mirrored. Distinct enough that a wrong quadrant cannot be mistaken for the
-// right one: top-left 255, top-right 170, bottom-left 85, bottom-right 0.
-static std::shared_ptr<std::vector<unsigned char>> make_quadrant_marker_png(size_t w = 32, size_t h = 32)
-{
-    std::vector<uint8_t> pixels(w * h);
-    for (size_t y = 0; y < h; ++y)
-        for (size_t x = 0; x < w; ++x)
-            pixels[y * w + x] = (y < h / 2) ? ((x < w / 2) ? 255 : 170) : ((x < w / 2) ? 85 : 0);
-    const boost::filesystem::path tmp_path = boost::filesystem::temp_directory_path()
-        / boost::filesystem::unique_path("texdisp_test_%%%%%%%%.png");
-    REQUIRE(Slic3r::png::write_gray_to_file(tmp_path.string(), w, h, pixels));
-
-    std::vector<unsigned char> bytes;
-    {
-        std::ifstream ifs(tmp_path.string(), std::ios::binary);
-        bytes.assign(std::istreambuf_iterator<char>(ifs), std::istreambuf_iterator<char>());
-    }
-    boost::system::error_code ec;
-    boost::filesystem::remove(tmp_path, ec);
-
-    REQUIRE_FALSE(bytes.empty());
-    return std::make_shared<std::vector<unsigned char>>(std::move(bytes));
-}
-
-TEST_CASE("baking an asymmetric image puts the top of the image at the top of the model", "[TextureDisplacement]")
-{
-    // An upright wall in the plane y = 0, facing -Y, tessellated so that each of the image's four
-    // quadrants gets a vertex at its centre. A flat sheet rather than a cube because every vertex
-    // normal is then exactly the face normal, which is what makes the expected depth below an exact
-    // number instead of a tri-planar blend of three of them.
-    constexpr int   STEPS = 4;    // cells per side, so 5x5 vertices
-    constexpr float SPAN  = 20.f; // mm, the wall's width and height
-    indexed_triangle_set wall;
-    for (int j = 0; j <= STEPS; ++j)
-        for (int i = 0; i <= STEPS; ++i)
-            wall.vertices.emplace_back(-SPAN / 2.f + SPAN * float(i) / float(STEPS), 0.f,
-                                       SPAN * float(j) / float(STEPS));
-    const auto at = [](int i, int j) { return j * (STEPS + 1) + i; };
-    for (int j = 0; j < STEPS; ++j)
-        for (int i = 0; i < STEPS; ++i) {
-            // Wound so that (+x) x (+z) = -y: the wall faces -Y, away from the origin.
-            wall.indices.emplace_back(at(i, j), at(i + 1, j), at(i + 1, j + 1));
-            wall.indices.emplace_back(at(i, j), at(i + 1, j + 1), at(i, j + 1));
-        }
-
-    TextureDisplacementFacetsData facets{};
-    facets[0] = paint_whole_mesh(wall);
-
-    TextureDisplacementLayer layer;
-    layer.slot              = 0;
-    layer.projection_method = TextureProjectionMethod::Triplanar;
-    layer.image_data        = make_quadrant_marker_png();
-    layer.depth_mm          = 2.f;
-    // The wall is 20 mm across and one tile is 40 mm, so it covers the middle half of the image in
-    // both axes: the quadrant boundaries land on x = 0 and z = 10, and the probed vertices sit a
-    // whole number of texels away from both.
-    layer.tiling_scale      = 40.f;
-    layer.offset            = Vec2f(0.5f, 0.75f);
-    // A single decal rather than a repeat, so that getting the orientation wrong cannot be masked by
-    // the wrap bringing the flipped coordinate back into the image at a plausible-looking row. With
-    // tiling off, uv stays inside [0.25, 0.75] in both axes only while v runs the right way.
-    layer.tile_enabled      = false;
-
-    const indexed_triangle_set result = build_texture_displacement(wall, { layer }, facets, classic_options());
-    REQUIRE(result.vertices.size() == wall.vertices.size());
-
-    // Seen from outside this face the viewer's right is +X and their up is +Z, so the image's
-    // top-left quadrant has to land at low x and high z. Each entry: the vertex, and the image value
-    // whose quadrant it must have read.
-    const std::array<std::tuple<const char *, int, int, int>, 4> expected = { {
-        { "top-left (255)", 1, 3, 255 },
-        { "top-right (170)", 3, 3, 170 },
-        { "bottom-left (85)", 1, 1, 85 },
-        { "bottom-right (0)", 3, 1, 0 },
-    } };
-
-    for (const auto &[name, i, j, value] : expected) {
-        DYNAMIC_SECTION("quadrant " << name)
-        {
-            const size_t vi = size_t(at(i, j));
-            // The whole displacement is along -Y, so this is the relief's height at that vertex.
-            const float raised = wall.vertices[vi].y() - result.vertices[vi].y();
-            INFO("vertex at " << wall.vertices[vi].x() << ", " << wall.vertices[vi].z());
-            CHECK_THAT(raised, WithinAbs(layer.depth_mm * float(value) / 255.f, 1e-3f));
-            // Nothing moved sideways or vertically: a mirrored or rotated basis would still have
-            // displaced along the normal, so this is here to catch the relief leaning instead.
-            CHECK_THAT(result.vertices[vi].x(), WithinAbs(wall.vertices[vi].x(), 1e-4f));
-            CHECK_THAT(result.vertices[vi].z(), WithinAbs(wall.vertices[vi].z(), 1e-4f));
-        }
-    }
-}
-
 TEST_CASE("The Cylindrical/Spherical patch frame is the bake's own, so a preview can share it", "[TextureDisplacement]")
 {
     // The fast preview reconstructs these two projections in the fragment shader and needs the very