Helix: draw the thing, then let the numbers be dragged

grep -i helix over the viewport code returned nothing at all. The tool was four
coupled numbers and a Confirm button — you typed radius, pitch, height and taper
blind and pressed OK to find out what you had made. So this is not only the
charter's L2 failure; the tool had no visible state whatsoever while it was open.

Adds a plane-anchored helix gizmo built on the datum-plane gizmo as its template,
being the closest existing thing: also plane-anchored, also driven by a card while
the sketch tool is inactive, also a render / hit-test / drag triad.

It draws the live curve and the axis, and puts a handle on each of the three
lengths: radius on the base circle, height at the top of the axis, pitch at the
end of the first turn — which is exactly where one pitch of rise lands, so the
handle means what it is standing on. Below one full turn the pitch handle moves
to the end of the curve rather than floating off a curve that does not exist yet.

Taper and handedness stay on the card. One is a shape modifier and the other a
flag; L2 governs numbers you can point at.

A drag reports the whole (radius, pitch, height) triple rather than one value,
because pitch and height are coupled through the turn count and writing one alone
would redraw a stale curve. The callback re-feeds the gizmo directly instead of
going through refresh_preview(), since Helix takes the produces-no-solid early
return and refresh_preview would rewrite the status line on every mouse move.

REVIEW CATCH, fixed here: the first cut read taper as a fraction of the radius
consumed over the turn count. It is an ANGLE IN DEGREES — helix_spine() builds a
Geom_ConicalSurface of half-angle taper and takes the top radius as R+H*tan(taper),
growing with the height risen. The wrong reading drew a preview that collapsed to
a point for any non-zero taper while the committed feature was perfectly fine. A
preview that lies is worse than no preview, which is what this commit replaced.

Reviewed and compiled (libslic3r_gui, RC=0); not exercised. snaporca-i3jc.

src/slic3r/GUI/DesignCanvas.cpp

@@ -843,6 +843,24 @@ void DesignCanvas::set_on_datum_offset_changed(std::function<void(double)> cb)
     m_sketch_tool.on_datum_offset_changed = std::move(cb);
 }
 
+void DesignCanvas::set_helix_gizmo(const SketchPlane& plane, double radius, double pitch,
+                                   double height, double taper, bool left_handed)
+{
+    m_sketch_tool.set_helix_gizmo(plane, radius, pitch, height, taper, left_handed);
+    request_repaint();
+}
+
+void DesignCanvas::clear_helix_gizmo()
+{
+    m_sketch_tool.clear_helix_gizmo();
+    request_repaint();
+}
+
+void DesignCanvas::set_on_helix_changed(std::function<void(double, double, double)> cb)
+{
+    m_sketch_tool.on_helix_changed = std::move(cb);
+}
+
 void DesignCanvas::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                                 std::vector<std::string> labels)
 {

src/slic3r/GUI/DesignCanvas.hpp

@@ -170,6 +170,10 @@ public:
     void clear_datum_gizmo();
     void set_on_datum_size_changed(std::function<void(double, double)> cb);
     void set_on_datum_offset_changed(std::function<void(double)> cb);
+    void set_helix_gizmo(const SketchPlane& plane, double radius, double pitch, double height,
+                         double taper, bool left_handed);          // helix curve + 3 drag handles
+    void clear_helix_gizmo();
+    void set_on_helix_changed(std::function<void(double, double, double)> cb);
     void set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                        std::vector<std::string> labels = {});   // clickable labelled reference planes
     void clear_base_pick();

src/slic3r/GUI/DesignPanel.cpp

@@ -3534,6 +3534,16 @@ DesignPanel::DesignPanel(wxWindow* parent)
         m_viewport->request_repaint();
     });
 
+    // Helix handles: a drag reports the whole triple, since pitch and height are coupled
+    // through the turn count and reading one without the others would show a stale curve.
+    m_viewport->set_on_helix_changed([this](double radius, double pitch, double height) {
+        if (m_helix_radius) m_helix_radius->SetValue(radius);
+        if (m_helix_pitch)  m_helix_pitch->SetValue(pitch);
+        if (m_helix_height) m_helix_height->SetValue(height);
+        update_helix_gizmo();      // re-feed so the curve follows the drag
+        m_viewport->request_repaint();
+    });
+
     // Clicking a ghost base plane sets the base graphically (replaces the dropdown). A base pick
     // drops any offset-from-face choice so the picked base plane wins, then re-resolves the preview.
     m_viewport->set_on_datum_base_picked([this](int base) {
@@ -9100,6 +9110,18 @@ void DesignPanel::update_datum_gizmo()
     update_reference_planes();   // base ghosts (origins + datums) follow the tool/model state
 }
 
+void DesignPanel::update_helix_gizmo()
+{
+    if (!m_viewport) return;
+    if (m_active != Tool::Helix) { m_viewport->clear_helix_gizmo(); return; }
+    m_viewport->set_helix_gizmo(plane_from_choice(m_helix_plane->GetSelection()),
+                                m_helix_radius ? m_helix_radius->GetValue() : 0.0,
+                                m_helix_pitch  ? m_helix_pitch->GetValue()  : 1.0,
+                                m_helix_height ? m_helix_height->GetValue() : 0.0,
+                                m_helix_taper  ? m_helix_taper->GetValue()  : 0.0,
+                                m_helix_left_handed && m_helix_left_handed->GetValue());
+}
+
 // Onshape default planes: the XY/XZ/YZ reference planes are persistent, transparent, labelled, and
 // larger than the bed — shown as the FALLBACK when there is no object yet. When the Plane tool is
 // open they additionally surface existing datums so a base can be picked. Single authority for the
@@ -9166,6 +9188,7 @@ void DesignPanel::refresh_preview()
         for (wxButton* b : m_confirm_btns) if (b) b->Enable(true);
         m_status->Refresh();
         update_datum_gizmo();   // Plane card: show/refresh the in-canvas resize handles
+        update_helix_gizmo();   // Helix card: draw the live curve + drag handles (no solid ghost)
         return;
     }
 
@@ -9272,6 +9295,8 @@ void DesignPanel::refresh_preview()
     update_pattern_gizmo();
     // Datum-plane resize handles (self-gates: only while the Plane card is open).
     update_datum_gizmo();
+    // Helix curve + handles (self-gates: only while the Helix card is open).
+    update_helix_gizmo();
     update_operand_highlight();
 }
 

src/slic3r/GUI/DesignPanel.hpp

@@ -272,6 +272,7 @@ private:
     void       update_operand_highlight(); // Boolean/Sweep/Loft operand tinting on the canvas
     void       update_pattern_gizmo();    // linear spacing arrow / circular angle-arc (Pattern card)
     void       update_datum_gizmo();      // resize handles on the datum plane being created/edited (C3)
+    void       update_helix_gizmo();      // live helix curve + radius/height/pitch handles (Helix card)
     void       refresh_datum_planes();    // push resolved datum frames + per-plane u/v extents to viewport
     void       refresh_mate_connectors(); // push connector frames so verse + polarity are visible
     void       update_reference_planes(); // persistent XY/XZ/YZ reference planes (fallback when no object)

src/slic3r/GUI/DesignSketchTool.cpp

@@ -3738,6 +3738,182 @@ void DesignSketchTool::drag_datum_handle(GLCanvas3D& canvas, const wxMouseEvent&
     if (on_datum_size_changed) on_datum_size_changed(m_dz_usize, m_dz_vsize);
 }
 
+// ---- Helix gizmo (plane-anchored curve + 3 drag handles) --------------------------------
+void DesignSketchTool::set_helix_gizmo(const SketchPlane& plane, double radius, double pitch,
+                                       double height, double taper, bool left_handed)
+{
+    m_hx_active = true;
+    m_hx_plane  = plane;
+    m_hx_radius = radius;
+    m_hx_pitch  = pitch;
+    m_hx_height = height;
+    m_hx_taper  = taper;
+    m_hx_left   = left_handed;
+}
+
+void DesignSketchTool::clear_helix_gizmo()
+{
+    m_hx_active = false;
+    m_hx_drag   = -1;
+}
+
+// Curve point at parameter t (t in turns): angle 2*pi*t, negated when left-handed, rising one
+// pitch per turn along the plane normal.
+//
+// Taper is an ANGLE IN DEGREES and must be read the way the kernel reads it. CadDocument's
+// helix_spine() builds a Geom_ConicalSurface of half-angle taper and computes the top radius as
+// R + H*tan(taper), so the radius grows with the HEIGHT RISEN, not as a fraction of R consumed
+// over the turn count. Getting that wrong draws a preview that collapses to a point for any
+// non-zero taper while the committed feature is fine — a preview that lies is worse than none.
+Vec3d DesignSketchTool::helix_point(double t) const
+{
+    const Vec3d O = m_hx_plane.origin;
+    const Vec3d n = m_hx_plane.normal.normalized();
+    const Vec3d u = m_hx_plane.x_axis.normalized();
+    const Vec3d v = m_hx_plane.y_axis.normalized();
+    const double a = (m_hx_left ? -1.0 : 1.0) * 2.0 * M_PI * t;
+    const double z = m_hx_pitch * t;                      // height risen at this parameter
+    double rt = m_hx_radius + z * std::tan(m_hx_taper * M_PI / 180.0);
+    // The kernel REFUSES a taper that drives the radius negative before the full height; the
+    // preview shows it collapsing instead, so the user can see which value did it.
+    if (rt < 0.0) rt = 0.0;
+    return O + u * (rt * std::cos(a)) + v * (rt * std::sin(a)) + n * z;
+}
+
+// Draw the live helix as a connected camera-facing ribbon, a dim axis line, and three square
+// handles (radius on the base circle, height on the axis top, pitch at the end of the first turn).
+void DesignSketchTool::render_helix_gizmo()
+{
+    if (!m_hx_active) return;
+    using EPT = GLModel::Geometry::EPrimitiveType;
+    using EVL = GLModel::Geometry::EVertexLayout;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const Vec3d right = cam.get_dir_right().normalized();
+    const Vec3d up    = cam.get_dir_up().normalized();
+    const Vec3d vd    = cam.get_dir_forward();
+    const double upp  = 1.0 / std::max(cam.get_zoom(), 1e-6);
+    const double hs   = 6.0 * upp;                       // handle half-size (~6 px)
+    const double hw   = 1.5 * upp;                       // ribbon half-width
+    const Vec3d O     = m_hx_plane.origin;
+    const Vec3d n     = m_hx_plane.normal.normalized();
+    const double turns = m_hx_pitch > 1e-9 ? m_hx_height / m_hx_pitch : 0.0;
+
+    // Curve ribbon: connected thin camera-facing quads over t in [0, turns].
+    const int segs = std::min(2048, std::max(48, int(turns * 32.0)));
+    GLModel::Geometry curve; curve.format = { EPT::Triangles, EVL::P3 };
+    unsigned int cb = 0;
+    auto add_seg = [&](const Vec3d& a, const Vec3d& b) {
+        Vec3d dir = b - a; if (dir.norm() < 1e-9) return; dir.normalize();
+        Vec3d off = dir.cross(vd);
+        if (off.norm() < 1e-9) off = dir.cross(up);
+        if (off.norm() < 1e-9) return;
+        off.normalize(); off *= hw;
+        curve.add_vertex((Vec3f)(a + off).cast<float>()); curve.add_vertex((Vec3f)(b + off).cast<float>());
+        curve.add_vertex((Vec3f)(b - off).cast<float>()); curve.add_vertex((Vec3f)(a - off).cast<float>());
+        curve.add_triangle(cb, cb + 1, cb + 2); curve.add_triangle(cb, cb + 2, cb + 3); cb += 4;
+    };
+    for (int i = 0; i < segs; ++i)
+        add_seg(helix_point(turns * i / segs), helix_point(turns * (i + 1) / segs));
+
+    // Axis: a dim line from the plane origin to the top of the helix.
+    const Vec3d top = O + n * m_hx_height;
+    GLModel::Geometry axis; axis.format = { EPT::Triangles, EVL::P3 };
+    {
+        Vec3d dir = top - O;
+        if (dir.norm() > 1e-9) {
+            dir.normalize();
+            Vec3d off = dir.cross(vd);
+            if (off.norm() < 1e-9) off = dir.cross(up);
+            if (off.norm() > 1e-9) {
+                off.normalize(); off *= hw * 0.6;
+                axis.add_vertex((Vec3f)(O + off).cast<float>()); axis.add_vertex((Vec3f)(top + off).cast<float>());
+                axis.add_vertex((Vec3f)(top - off).cast<float>()); axis.add_vertex((Vec3f)(O - off).cast<float>());
+                axis.add_triangle(0, 1, 2); axis.add_triangle(0, 2, 3);
+            }
+        }
+    }
+
+    // Three handles: 0=radius (t=0), 1=height (axis top), 2=pitch (end of first turn, or the
+    // whole curve if shorter than one turn so the handle never floats off a missing curve).
+    const Vec3d hpts[3] = { helix_point(0.0), top,
+                            helix_point(m_hx_height < m_hx_pitch ? turns : 1.0) };
+    const ColorRGBA hcol[3] = { ColorRGBA(1.0f, 0.72f, 0.28f, 1.0f),   // radius — amber
+                                ColorRGBA(0.45f, 0.86f, 1.0f, 1.0f),   // height — cyan
+                                ColorRGBA(0.30f, 0.80f, 0.34f, 1.0f) }; // pitch — green
+    const ColorRGBA hot(1.0f, 0.85f, 0.2f, 1.0f);
+
+    glsafe(::glDisable(GL_DEPTH_TEST));
+    if (cb > 0) {
+        GLModel m; m.init_from(std::move(curve));
+        m.set_color(ColorRGBA(1.0f, 0.62f, 0.16f, 0.9f));   // CAD amber helix curve
+        m.render();
+    }
+    if (!axis.vertices.empty()) {
+        GLModel m; m.init_from(std::move(axis));
+        m.set_color(ColorRGBA(0.42f, 0.46f, 0.52f, 0.55f));   // dim grey axis
+        m.render();
+    }
+    for (int i = 0; i < 3; ++i) {
+        const Vec3d ctr = hpts[i];
+        const Vec3d q0 = ctr - right * hs - up * hs, q1 = ctr + right * hs - up * hs,
+                    q2 = ctr + right * hs + up * hs, q3 = ctr - right * hs + up * hs;
+        GLModel::Geometry sq; sq.format = { EPT::Triangles, EVL::P3 };
+        sq.add_vertex((Vec3f)q0.cast<float>()); sq.add_vertex((Vec3f)q1.cast<float>());
+        sq.add_vertex((Vec3f)q2.cast<float>()); sq.add_vertex((Vec3f)q3.cast<float>());
+        sq.add_triangle(0, 1, 2); sq.add_triangle(0, 2, 3);
+        GLModel m; m.init_from(std::move(sq));
+        m.set_color(m_hx_drag == i ? hot : hcol[i]);
+        m.render();
+    }
+}
+
+bool DesignSketchTool::hit_test_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const
+{
+    if (!m_hx_active) return false;
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const Camera& cam = wxGetApp().plater()->get_camera();
+    const double tol = 9.0 / std::max(cam.get_zoom(), 1e-6);   // ~9 px in world units
+    const Vec3d O = m_hx_plane.origin;
+    const Vec3d n = m_hx_plane.normal.normalized();
+    const double turns = m_hx_pitch > 1e-9 ? m_hx_height / m_hx_pitch : 0.0;
+    const Vec3d hpts[3] = { helix_point(0.0), O + n * m_hx_height,
+                            helix_point(m_hx_height < m_hx_pitch ? turns : 1.0) };
+    double best = tol; which = -1;
+    for (int i = 0; i < 3; ++i) {
+        const Vec3d w  = hpts[i] - ro;
+        const double t = w.dot(rd) / std::max(rd.dot(rd), 1e-12);
+        const double d = (w - rd * t).norm();
+        if (d < best) { best = d; which = i; }
+    }
+    return which >= 0;
+}
+
+// Drag a handle: radius = cursor's in-plane distance from the origin, height/pitch = the signed
+// distance of the cursor's closest axis point. All fire the full (radius, pitch, height) triple.
+void DesignSketchTool::drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which)
+{
+    const Linef3 r = canvas.mouse_ray(Point(evt.GetX(), evt.GetY()));
+    const Vec3d ro = r.a, rd = r.b - r.a;
+    const SketchPlane& p = m_hx_plane;
+    const Vec3d O = p.origin, n = p.normal.normalized();
+
+    if (which == 0) {                                          // radius: in-plane distance from O
+        const Vec2d lp = p.project(ro, rd);
+        m_hx_radius = std::max(0.01, lp.norm());
+    } else {                                                   // height/pitch: signed distance along n
+        const Vec3d e   = n;
+        const Vec3d w0  = O - ro;
+        const double a  = e.dot(e), b = e.dot(rd), c = rd.dot(rd), dd = e.dot(w0), ee = rd.dot(w0);
+        const double denom = a * c - b * b;
+        if (std::abs(denom) < 1e-7) return;                    // camera ∥ axis: leave value as-is
+        const double s = (b * ee - c * dd) / denom;            // signed distance along the axis
+        if (which == 1) m_hx_height = std::max(0.0, s);
+        else            m_hx_pitch  = std::max(0.01, s);       // zero/negative pitch divides by zero
+    }
+    if (on_helix_changed) on_helix_changed(m_hx_radius, m_hx_pitch, m_hx_height);
+}
+
 // ---- Reference/base planes (Onshape-style default planes) -----------------------------
 void DesignSketchTool::set_base_pick(std::vector<SketchPlane> planes, std::vector<int> bases,
                                      std::vector<std::string> labels)
@@ -7159,6 +7335,7 @@ void DesignSketchTool::render(GLCanvas3D& canvas)
         render_solid_highlight();
         if (m_dbp_active) render_base_pick();
         if (m_dz_active) render_datum_gizmo();
+        if (m_hx_active) render_helix_gizmo();
         if (m_ex_active) render_extrude_gizmo();
         if (m_mv_active) render_move_gizmo();
         if (m_fl_active) render_fillet_gizmo();
@@ -7966,6 +8143,21 @@ bool DesignSketchTool::on_mouse_impl(wxMouseEvent& evt, GLCanvas3D& canvas)
                 }
             }
         }
+        // Helix gizmo: radius/height/pitch handles on the live curve, while the Helix card is open.
+        if (m_hx_active) {
+            if (m_hx_drag >= 0 && evt.Dragging() && evt.LeftIsDown()) {
+                drag_helix_handle(canvas, evt, m_hx_drag);
+                return true;
+            }
+            if (evt.LeftUp() && m_hx_drag >= 0) { m_hx_drag = -1; return true; }
+            if (evt.LeftDown()) {
+                int which = -1;
+                if (hit_test_helix_handle(canvas, evt, which)) {
+                    m_hx_drag = which; m_hx_press_x = evt.GetX(); m_hx_press_y = evt.GetY();
+                    return true;
+                }
+            }
+        }
         // Datum base picker: HOVER highlight only here. The CLICK is handled at the very end of the
         // selection fall-through (below), so picking existing geometry (committed sketch loops,
         // solid faces/edges) always wins over a base-plane click — the planes never block selection.

src/slic3r/GUI/DesignSketchTool.hpp

@@ -119,7 +119,7 @@ public:
                                       || m_show_planes || m_show_axes
                                       || m_ex_active || m_mv_active || m_fl_active
                                       || m_hl_active || m_th_active || m_sh_active
-                                      || m_dr_active || m_ct_active || m_dz_active || m_dbp_active; }
+                                      || m_dr_active || m_ct_active || m_dz_active || m_dbp_active || m_hx_active; }
 
     // View helpers: the 3 world origin planes (XY/XZ/YZ) and the world axis triad, each
     // shown/hidden by a toggle (keys P / A). Off by default so the idle scene stays clean.
@@ -204,6 +204,16 @@ public:
     std::function<void(double usize, double vsize)> on_datum_size_changed;
     std::function<void(double offset)>              on_datum_offset_changed;
 
+    // Visual Helix gizmo. The Helix tool is a DesignPanel docked card (sketch tool NOT active),
+    // so the panel resolves the axis plane and feeds the live parameters here; the tool draws
+    // the helix curve itself plus three handles — radius on the base circle, height at the top
+    // of the axis, pitch at the end of the first turn. Taper and handedness stay on the card:
+    // one is a shape modifier and the other is a flag, and L2 governs numbers you can point at.
+    void set_helix_gizmo(const SketchPlane& plane, double radius, double pitch, double height,
+                         double taper, bool left_handed);
+    void clear_helix_gizmo();
+    std::function<void(double radius, double pitch, double height)> on_helix_changed;
+
     // Graphical base/origin pick: while the Plane card is open, the candidate base planes
     // (XY/XZ/YZ origin planes + existing datums) draw as translucent clickable ghosts. A click
     // on one fires on_datum_base_picked(base) with that plane's base index (0/1/2 or 3+N).
@@ -1013,6 +1023,22 @@ private:
     void  render_datum_gizmo();
     bool  hit_test_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
     void  drag_datum_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
+    // Helix gizmo state (plane-anchored curve + 3 drag handles). Fed by the panel while the
+    // Helix card is open (sketch tool NOT active); the tool draws the live helix plus a handle
+    // on each length parameter (radius/height/pitch). Taper and handedness stay on the card.
+    bool        m_hx_active{false};
+    SketchPlane m_hx_plane;                  // axis = plane normal, base circle in the plane
+    double      m_hx_radius{10.0};
+    double      m_hx_pitch{2.0};
+    double      m_hx_height{20.0};
+    double      m_hx_taper{0.0};             // DEGREES (cone half-angle), as the kernel reads it
+    bool        m_hx_left{false};
+    int         m_hx_drag{-1};               // 0=radius, 1=height, 2=pitch, -1 none
+    int         m_hx_press_x{0}, m_hx_press_y{0};
+    Vec3d helix_point(double t) const;       // curve point at parameter t (shared render/hit/drag)
+    void  render_helix_gizmo();
+    bool  hit_test_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int& which) const;
+    void  drag_helix_handle(GLCanvas3D& canvas, const wxMouseEvent& evt, int which);
     // Datum base picker (translucent clickable origin/datum planes)
     bool        m_dbp_active{false};
     std::vector<SketchPlane>  m_dbp_planes;