Texture displacement: save layers, textures and paint in the .3mf (#16148)

## General Nothing about texture displacement was written to the `.3mf`, so a painted relief did not survive closing the project. Everything the user set up is saved now, so a project reopens with the relief intact and still editable. ### What is saved - The layer stack: every per-layer setting (depth, midlevel, smoothing, tiling, projection blend mode, colour) and the per-volume options - Each layer's texture, as a file in the archive (why? because user might want to move .3mf to another computer where custom textures are missing, or he saves .3mf then deletes textures, and returns back to .3mf) - The painted region, one mask per layer slot - The UV work: LSCM seams, island placement, per-vertex overrides - Editor state: the selected layer and Standard/Pro, so the panel reopens where it was left ### What is not saved - The preview mesh. It is a second copy of the model in the file, for something the app rebuilds quickly on reopen. - Panel docked/undocked, which goes to the application config instead ## Format - `<volume id>.json` - the layer stack and the per-volume options - `<volume id>_<slot>.png` - each layer's texture, referenced from the JSON through `path_in_3mf` Paint masks ride along as one per-triangle attribute per slot (`paint_texture_0..7`), beside the attributes the existing paint tools already write. ## Compatibility Both ways: - an older build ignores what it does not know and still opens the project, losing only the relief - a newer build finds nothing in an older project and leaves the volume as today.
2026-10-12 18:31:18 +00:00 · 2026-10-12 20:00:17 +08:00
parent cccf53850e d8cae3268a
commit 08f2037cbd
7 changed files with 838 additions and 18 deletions
@@ -22,6 +22,7 @@
 #include "libslic3r/BrimEarsPoint.hpp"
 #include "libslic3r/Config.hpp"
 #include "libslic3r/CustomGCode.hpp"
+#include "libslic3r/TextureDisplacement.hpp"
 #include "libslic3r_version.h"

 #include "bbs_3mf.hpp"
@@ -354,6 +355,13 @@ static constexpr const char* CUSTOM_SUPPORTS_ATTR = "paint_supports";
 static constexpr const char* CUSTOM_FUZZY_SKIN_ATTR  = "paint_fuzzy_skin";
 static constexpr const char* CUSTOM_SEAM_ATTR = "paint_seam";
 static constexpr const char* MMU_SEGMENTATION_ATTR = "paint_color";
+// Texture displacement. One paint mask per layer slot, mirroring paint_color; the layer stack itself is
+// a JSON file in the archive, named by the volume metadata key below (see add_texture_displacement()).
+static constexpr const char* TEXTURE_DISPLACEMENT_ATTRS[Slic3r::TEXTURE_DISPLACEMENT_MAX_LAYERS] = {
+    "paint_texture_0", "paint_texture_1", "paint_texture_2", "paint_texture_3",
+    "paint_texture_4", "paint_texture_5", "paint_texture_6", "paint_texture_7" };
+static constexpr const char* TEXTURE_DISPLACEMENT_KEY = "texture_displacement";
+static constexpr const char* TEXTURE_DISPLACEMENT_DIR = "Metadata/texture_displacement/";
 // BBS
 static constexpr const char* FACE_PROPERTY_ATTR = "face_property";

@@ -847,6 +855,9 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            std::vector<std::string> custom_seam;
            std::vector<std::string> mmu_segmentation;
            std::vector<std::string> fuzzy_skin;
+            // One per texture displacement layer slot, indexed like `triangles` but stored only as far as the
+            // slot's last painted triangle: empty when the slot has no paint, which is nearly every file.
+            std::vector<std::string> texture_displacement[TEXTURE_DISPLACEMENT_MAX_LAYERS];
            // BBS
            std::vector<std::string> face_properties;

@@ -867,6 +878,8 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                custom_seam.clear();
                mmu_segmentation.clear();
                fuzzy_skin.clear();
+                for (std::vector<std::string> &slot : texture_displacement)
+                    slot.clear();
            }
        };

@@ -1200,6 +1213,11 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
        /*IdToSlaSupportPointsMap m_sla_support_points;
        IdToSlaDrainHolesMap    m_sla_drain_holes;*/
        PathToEmbossShapeFileMap m_path_to_emboss_shape_files;
+        // Texture displacement: every file under Metadata/texture_displacement/, by archive path. Volumes
+        // are built only after the whole archive has been walked, so by the time a volume names its JSON
+        // every file it could refer to is already in here, whatever order the archive happened to be in.
+        std::map<std::string, std::string> m_texture_displacement_files;
+        void _apply_texture_displacement(ModelVolume &volume, const std::string &json_path);
        std::string m_curr_metadata_name;
        std::string m_curr_characters;
        std::string m_name;
@@ -2073,6 +2091,13 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                else if (_is_svg_shape_file(name)) {
                    _extract_embossed_svg_shape_file(name, archive, stat);
                }
+                else if (boost::algorithm::istarts_with(name, TEXTURE_DISPLACEMENT_DIR)) {
+                    std::string contents(stat.m_uncomp_size, '\0');
+                    if (mz_zip_reader_extract_to_mem(&archive, stat.m_file_index, contents.data(), stat.m_uncomp_size, 0))
+                        m_texture_displacement_files.emplace(name, std::move(contents));
+                    else
+                        add_error("Error while reading texture displacement data");
+                }
                else if (!dont_load_config && boost::algorithm::iequals(name, SLICE_INFO_CONFIG_FILE)) {
                    m_parsing_slice_info = true;
                    //extract slice info from archive
@@ -3310,6 +3335,45 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
        }
    }*/

+    // Restores one volume's texture displacement stack from the JSON it named. Called while the volume is
+    // being built, which is after the whole archive has been walked - so every file it can refer to is
+    // already extracted, and no deferral is needed.
+    //
+    // A missing or malformed JSON leaves the volume with no layers but keeps the paint mask it already
+    // loaded, which is the same state as a project saved by a build without the feature: recoverable by
+    // picking the texture again rather than a hard failure.
+    void _BBS_3MF_Importer::_apply_texture_displacement(ModelVolume &volume, const std::string &json_path)
+    {
+        const auto json = m_texture_displacement_files.find(json_path);
+        if (json == m_texture_displacement_files.end()) {
+            add_error("Missing texture displacement data: " + json_path);
+            return;
+        }
+        std::vector<TextureDisplacementLayer> layers;
+        TextureDisplacementOptions            options;
+        if (!texture_displacement_layers_from_json(json->second, layers, options)) {
+            add_error("Malformed texture displacement data: " + json_path);
+            return;
+        }
+        // The archive is the only source of a layer's pixels. `path` comes from the project file, so loading
+        // the project must never read the file it names: that would let whoever made the project pick any
+        // local (or, on Windows, network) file to read, and the next save would embed it in the archive.
+        // `path` stays a label of where the texture came from; a layer the archive carries no image for
+        // loads without one, its settings intact, until the user picks a texture again.
+        for (TextureDisplacementLayer &layer : layers) {
+            if (layer.path_in_3mf.empty())
+                continue;
+            const auto image = m_texture_displacement_files.find(layer.path_in_3mf);
+            if (image == m_texture_displacement_files.end()) {
+                add_error("Missing texture displacement image: " + layer.path_in_3mf);
+                continue;
+            }
+            layer.image_data = std::make_shared<std::vector<unsigned char>>(image->second.begin(), image->second.end());
+        }
+        volume.texture_displacement_layers  = std::move(layers);
+        volume.texture_displacement_options = options;
+    }
+
    void _BBS_3MF_Importer::_extract_embossed_svg_shape_file(const std::string &filename, mz_zip_archive &archive, const mz_zip_archive_file_stat &stat){
        assert(m_path_to_emboss_shape_files.find(filename) == m_path_to_emboss_shape_files.end());
        auto file = std::make_unique<std::string>(stat.m_uncomp_size, '\0');
@@ -3966,6 +4030,12 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            m_curr_object->geometry.custom_seam.push_back(bbs_get_attribute_value_string(attributes, num_attributes, CUSTOM_SEAM_ATTR));
            m_curr_object->geometry.mmu_segmentation.push_back(bbs_get_attribute_value_string(attributes, num_attributes, MMU_SEGMENTATION_ATTR));
            m_curr_object->geometry.fuzzy_skin.push_back(bbs_get_attribute_value_string(attributes, num_attributes, CUSTOM_FUZZY_SKIN_ATTR));
+            for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS); ++slot)
+                if (const char *paint = bbs_get_attribute_value_charptr(attributes, num_attributes, TEXTURE_DISPLACEMENT_ATTRS[slot])) {
+                    std::vector<std::string> &mask = m_curr_object->geometry.texture_displacement[slot];
+                    mask.resize(m_curr_object->geometry.triangles.size());
+                    mask.back() = paint;
+                }
            // BBS
            m_curr_object->geometry.face_properties.push_back(bbs_get_attribute_value_string(attributes, num_attributes, FACE_PROPERTY_ATTR));
        }
@@ -5317,6 +5387,18 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                volume->mmu_segmentation_facets.touch();
                volume->fuzzy_skin_facets.shrink_to_fit();
                volume->fuzzy_skin_facets.touch();
+                for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS); ++slot) {
+                    const std::vector<std::string> &mask = sub_object->geometry.texture_displacement[slot];
+                    if (mask.empty())
+                        continue; // no triangle painted on this slot
+                    FacetsAnnotation &facets = volume->texture_displacement_facet(slot);
+                    facets.reserve(triangles_count);
+                    for (size_t i = 0; i < triangles_count && i < mask.size(); ++i)
+                        if (!mask[i].empty())
+                            facets.set_triangle_from_string(i, mask[i]);
+                    facets.shrink_to_fit();
+                    facets.touch();
+                }
            }

            volume->set_type(volume_data->part_type);
@@ -5332,6 +5414,8 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            for (const Metadata& metadata : volume_data->metadata) {
                if (metadata.key == NAME_KEY)
                    volume->name = metadata.value;
+                else if (metadata.key == TEXTURE_DISPLACEMENT_KEY)
+                    _apply_texture_displacement(*volume, metadata.value);
                //else if ((metadata.key == MODIFIER_KEY) && (metadata.value == "1"))
 				//	volume->set_type(ModelVolumeType::PARAMETER_MODIFIER);
 				//for old format
@@ -5496,12 +5580,28 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            volume->seam_facets.shrink_to_fit();
            volume->mmu_segmentation_facets.shrink_to_fit();

+            for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS); ++slot) {
+                const std::vector<std::string> &mask = geometry.texture_displacement[slot];
+                if (mask.empty())
+                    continue; // written by a build without the feature
+                FacetsAnnotation &facets = volume->texture_displacement_facet(slot);
+                facets.reserve(triangles_count);
+                for (size_t i = 0; i < triangles_count; ++i) {
+                    const size_t index = volume_data.first_triangle_id + i;
+                    if (index < mask.size() && !mask[index].empty())
+                        facets.set_triangle_from_string(i, mask[index]);
+                }
+                facets.shrink_to_fit();
+                facets.touch();
+            }
            volume->set_type(volume_data.part_type);

            // apply the remaining volume's metadata
            for (const Metadata& metadata : volume_data.metadata) {
                if (metadata.key == NAME_KEY)
                    volume->name = metadata.value;
+                else if (metadata.key == TEXTURE_DISPLACEMENT_KEY)
+                    _apply_texture_displacement(*volume, metadata.value);
                //else if ((metadata.key == MODIFIER_KEY) && (metadata.value == "1"))
 				//	volume->set_type(ModelVolumeType::PARAMETER_MODIFIER);
 				//for old format
@@ -5805,6 +5905,12 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
            current_object->geometry.custom_seam.push_back(bbs_get_attribute_value_string(attributes, num_attributes, CUSTOM_SEAM_ATTR));
            current_object->geometry.mmu_segmentation.push_back(bbs_get_attribute_value_string(attributes, num_attributes, MMU_SEGMENTATION_ATTR));
            current_object->geometry.fuzzy_skin.push_back(bbs_get_attribute_value_string(attributes, num_attributes, CUSTOM_FUZZY_SKIN_ATTR));
+            for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS); ++slot)
+                if (const char *paint = bbs_get_attribute_value_charptr(attributes, num_attributes, TEXTURE_DISPLACEMENT_ATTRS[slot])) {
+                    std::vector<std::string> &mask = current_object->geometry.texture_displacement[slot];
+                    mask.resize(current_object->geometry.triangles.size());
+                    mask.back() = paint;
+                }
            // BBS
            current_object->geometry.face_properties.push_back(bbs_get_attribute_value_string(attributes, num_attributes, FACE_PROPERTY_ATTR));
        }
@@ -6808,6 +6914,9 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
        stream << " <Default Extension=\"rels\" ContentType=\"application/vnd.openxmlformats-package.relationships+xml\"/>\n";
        stream << " <Default Extension=\"model\" ContentType=\"application/vnd.ms-package.3dmanufacturing-3dmodel+xml\"/>\n";
        stream << " <Default Extension=\"png\" ContentType=\"image/png\"/>\n";
+        stream << " <Default Extension=\"jpg\" ContentType=\"image/jpeg\"/>\n";
+        stream << " <Default Extension=\"jpeg\" ContentType=\"image/jpeg\"/>\n";
+        stream << " <Default Extension=\"json\" ContentType=\"application/json\"/>\n";
        stream << " <Default Extension=\"gcode\" ContentType=\"text/x.gcode\"/>\n";
        stream << "</Types>";

@@ -7232,10 +7341,14 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                            if (iter != m_shared_meshes.end())
                            {
                                const ModelVolume* shared_volume = iter->second.second;
+                                bool same_texture_paint = true;
+                                for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS) && same_texture_paint; ++slot)
+                                    same_texture_paint = shared_volume->texture_displacement_facet(slot).equals(volume->texture_displacement_facet(slot));
                                if ((shared_volume->supported_facets.equals(volume->supported_facets))
                                    && (shared_volume->seam_facets.equals(volume->seam_facets))
                                    && (shared_volume->mmu_segmentation_facets.equals(volume->mmu_segmentation_facets))
-                                    && (shared_volume->fuzzy_skin_facets.equals(volume->fuzzy_skin_facets)))
+                                    && (shared_volume->fuzzy_skin_facets.equals(volume->fuzzy_skin_facets))
+                                    && same_texture_paint)
                                {
                                    auto data = iter->second.first;
                                    const_cast<_BBS_3MF_Exporter *>(this)->m_volume_paths.insert({volume, {data->sub_path, data->volumes_objectID.find(iter->second.second)->second}});
@@ -7651,6 +7764,20 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                    output_buffer += "\"";
                }

+                // One attribute per texture displacement layer slot. Older readers ignore attributes they do
+                // not know, so a project written here still opens in a build without the feature - it just
+                // loses the paint, which is also all it could have done with it.
+                for (int slot = 0; slot < TEXTURE_DISPLACEMENT_MAX_LAYERS; ++slot) {
+                    const std::string texture_paint = volume->texture_displacement_facet(slot).get_triangle_as_string(i);
+                    if (texture_paint.empty())
+                        continue;
+                    output_buffer += " ";
+                    output_buffer += TEXTURE_DISPLACEMENT_ATTRS[slot];
+                    output_buffer += "=\"";
+                    output_buffer += texture_paint;
+                    output_buffer += "\"";
+                }
+
                // BBS
                if (i < its.properties.size()) {
                    std::string prop_str = its.properties[i].to_string();
@@ -8100,7 +8227,42 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
        return file_path;
    }

-    bool _BBS_3MF_Exporter::_add_model_config_file_to_archive(mz_zip_archive& archive, const Model& model, PlateDataPtrs& plate_data_list, const ObjectToObjectDataMap &objects_data, const DynamicPrintConfig& config, int export_plate_idx, bool save_gcode, bool use_loaded_id)
+    // Writes a volume's texture displacement stack into the archive and points the volume's metadata at it.
+// The layer settings go in as JSON and each layer's texture as the image file it was loaded from, both
+// referenced by path - the same split EmbossShape makes for its SVG. The image deliberately stays out of
+// the XML: it is binary and routinely megabytes, and base64 in an attribute would bloat the one file
+// every reader has to parse just to list the objects.
+static void add_texture_displacement(std::stringstream &stream, const ModelVolume &volume, mz_zip_archive &archive,
+                                     const std::string &id)
+{
+    if (volume.texture_displacement_layers.empty())
+        return;
+
+    // A copy, because path_in_3mf is only meaningful inside the archive being written and the volume
+    // being exported is const (and may be saved again, elsewhere, with different paths).
+    std::vector<TextureDisplacementLayer> layers = volume.texture_displacement_layers;
+    for (TextureDisplacementLayer &layer : layers) {
+        layer.path_in_3mf.clear();
+        if (!layer.image_data || layer.image_data->empty())
+            continue;
+        // Always .png: the importer converts whatever the user picked (jpg, bmp, ...) to an 8-bit
+        // greyscale PNG, so image_data is PNG whatever layer.path happens to be named.
+        const std::string path = std::string(TEXTURE_DISPLACEMENT_DIR) + id + "_" + std::to_string(layer.slot) + ".png";
+        // No deflate: a PNG is already compressed, so a second pass only costs time.
+        if (mz_zip_writer_add_mem(&archive, path.c_str(), layer.image_data->data(), layer.image_data->size(),
+                                  MZ_NO_COMPRESSION))
+            layer.path_in_3mf = path;
+    }
+
+    const std::string json      = texture_displacement_layers_to_json(layers, volume.texture_displacement_options);
+    const std::string json_path = std::string(TEXTURE_DISPLACEMENT_DIR) + id + ".json";
+    if (!mz_zip_writer_add_mem(&archive, json_path.c_str(), json.data(), json.size(), MZ_DEFAULT_COMPRESSION))
+        return;
+    stream << "      <" << METADATA_TAG << " " << KEY_ATTR << "=\"" << TEXTURE_DISPLACEMENT_KEY << "\" "
+           << VALUE_ATTR << "=\"" << xml_escape(json_path) << "\"/>\n";
+}
+
+bool _BBS_3MF_Exporter::_add_model_config_file_to_archive(mz_zip_archive& archive, const Model& model, PlateDataPtrs& plate_data_list, const ObjectToObjectDataMap &objects_data, const DynamicPrintConfig& config, int export_plate_idx, bool save_gcode, bool use_loaded_id)
    {
        std::stringstream stream;
        // Store mesh transformation in full precision, as the volumes are stored transformed and they need to be transformed back
@@ -8211,6 +8373,8 @@ void PlateData::parse_filament_info(GCodeProcessorResult *result)
                            if (const std::optional<EmbossShape> &es = volume->emboss_shape; es.has_value()) {
                                to_xml(stream, *es, *volume, archive, m_fullpath_sources);
                            }
+
+                            add_texture_displacement(stream, *volume, archive, std::to_string(volume->id().id));
                    
                            if (const std::optional<TextConfiguration> &tc = volume->text_configuration;
                                tc.has_value())
@@ -19,6 +19,7 @@
 #include <mutex>
 #include <numeric>
 #include <optional>
+#include "nlohmann/json.hpp"
 #include <queue>
 #include <ratio>
 #include <string>
@@ -5166,5 +5167,260 @@ indexed_triangle_set cut_mesh_at_steps(const indexed_triangle_set &mesh, const s
    return out;
 }

+// ---------------------------------------------------------------------------------------------
+// Project persistence. See the declarations in TextureDisplacement.hpp for why this is JSON rather
+// than the cereal stream next to them.
+// ---------------------------------------------------------------------------------------------
+namespace {
+
+nlohmann::json vec2_to_json(const Vec2f &v) { return nlohmann::json::array({ v.x(), v.y() }); }
+nlohmann::json vec3_to_json(const Vec3f &v) { return nlohmann::json::array({ v.x(), v.y(), v.z() }); }
+
+Vec2f vec2_from_json(const nlohmann::json &j, const Vec2f &fallback)
+{
+    if (!j.is_array() || j.size() != 2)
+        return fallback;
+    return Vec2f(j[0].get<float>(), j[1].get<float>());
+}
+Vec3f vec3_from_json(const nlohmann::json &j, const Vec3f &fallback)
+{
+    if (!j.is_array() || j.size() != 3)
+        return fallback;
+    return Vec3f(j[0].get<float>(), j[1].get<float>(), j[2].get<float>());
+}
+
+// Reads key `k` into `out` when it is present and of the expected type, leaving `out` alone otherwise.
+// That "leave it alone" is the whole point: every member starts at its struct default, so a project
+// written by an older build simply keeps the defaults for whatever it did not know about.
+template<class T> void read(const nlohmann::json &j, const char *k, T &out)
+{
+    const auto it = j.find(k);
+    if (it == j.end())
+        return;
+    try {
+        out = it->get<T>();
+    } catch (...) {
+    }
+}
+void read_enum(const nlohmann::json &j, const char *k, int &out)
+{
+    const auto it = j.find(k);
+    if (it != j.end() && it->is_number_integer())
+        out = it->get<int>();
+}
+
+} // namespace
+
+std::string texture_displacement_layers_to_json(const std::vector<TextureDisplacementLayer> &layers,
+                                                const TextureDisplacementOptions            &options)
+{
+    nlohmann::json root;
+    root["version"] = 1;
+
+    nlohmann::json &opt = root["options"];
+    opt["displace_border"]    = options.displace_border;
+    opt["smooth_enabled"]     = options.smooth_enabled;
+    opt["smooth_strength"]    = options.smooth_strength;
+    opt["smooth_iterations"]  = options.smooth_iterations;
+    opt["smooth_skip_border"] = options.smooth_skip_border;
+    opt["pipeline_v2"]        = options.pipeline_v2;
+    opt["v2_refine_mm"]       = options.v2_refine_mm;
+    opt["v2_regularize"]      = options.v2_regularize;
+    opt["v2_max_triangles_k"] = options.v2_max_triangles_k;
+    opt["v2_relocate"]        = options.v2_relocate;
+    opt["v2_flip_edges"]      = options.v2_flip_edges;
+    opt["color_mix_enabled"]  = options.color_mix_enabled;
+    opt["color_despeckle"]    = options.color_despeckle;
+    opt["color_mix_count"]    = options.color_mix_count;
+    opt["active_slot"]        = options.active_slot;
+    opt["panel_mode"]         = options.panel_mode;
+
+    nlohmann::json &arr = root["layers"];
+    arr                 = nlohmann::json::array();
+    for (const TextureDisplacementLayer &l : layers) {
+        nlohmann::json j;
+        j["slot"]        = l.slot;
+        j["name"]        = l.name;
+        j["path"]        = l.path;
+        j["path_in_3mf"] = l.path_in_3mf;
+
+        j["depth_mm"]     = l.depth_mm;
+        j["tiling_scale"] = l.tiling_scale;
+        j["rotation_deg"] = l.rotation_deg;
+        j["offset"]       = vec2_to_json(l.offset);
+        j["invert"]       = l.invert;
+        j["midlevel"]     = l.midlevel;
+        j["smoothing"]    = l.smoothing;
+
+        j["edge_smoothing"]        = l.edge_smoothing;
+        j["edge_smoothing_amount"] = l.edge_smoothing_amount;
+        j["auto_connect_islands"]  = l.auto_connect_islands;
+
+        j["tile_enabled"]      = l.tile_enabled;
+        j["tile_method"]       = int(l.tile_method);
+        j["projection_method"] = int(l.projection_method);
+        j["blend_mode"]        = int(l.blend_mode);
+        j["color_enabled"]     = l.color_enabled;
+
+        j["lscm_seam_angle_deg"] = l.lscm_seam_angle_deg;
+        j["island_padding_mm"]   = l.island_padding_mm;
+
+        j["view_project_right"]      = vec3_to_json(l.view_project_right);
+        j["view_project_up"]         = vec3_to_json(l.view_project_up);
+        j["view_project_projective"] = l.view_project_projective;
+        j["view_project_matrix"]     = l.view_project_matrix;
+
+        // Flat pairs rather than nested arrays: shorter, and the reader can simply ignore a trailing
+        // odd element instead of having to validate every sub-array.
+        nlohmann::json &seams = j["lscm_seam_edges"];
+        seams                 = nlohmann::json::array();
+        for (const auto &[a, b] : l.lscm_seam_edges) {
+            seams.push_back(a);
+            seams.push_back(b);
+        }
+
+        nlohmann::json &islands = j["islands"];
+        islands                 = nlohmann::json::array();
+        for (const TextureIsland &island : l.islands)
+            islands.push_back(nlohmann::json::array(
+                { island.offset.x(), island.offset.y(), island.rotation_deg, island.scale }));
+
+        j["island_groups"] = l.island_groups;
+
+        nlohmann::json &overrides = j["lscm_uv_overrides"];
+        overrides                 = nlohmann::json::array();
+        for (const auto &[key, uv] : l.lscm_uv_overrides)
+            overrides.push_back(nlohmann::json::array({ key, uv.x(), uv.y() }));
+
+        arr.push_back(std::move(j));
+    }
+    return root.dump();
+}
+
+bool texture_displacement_layers_from_json(const std::string                     &text,
+                                           std::vector<TextureDisplacementLayer> &layers,
+                                           TextureDisplacementOptions            &options)
+{
+    nlohmann::json root;
+    try {
+        root = nlohmann::json::parse(text);
+    } catch (...) {
+        return false;
+    }
+    if (!root.is_object())
+        return false;
+
+    TextureDisplacementOptions out_options;
+    if (const auto it = root.find("options"); it != root.end() && it->is_object()) {
+        const nlohmann::json &opt = *it;
+        read(opt, "displace_border", out_options.displace_border);
+        read(opt, "smooth_enabled", out_options.smooth_enabled);
+        read(opt, "smooth_strength", out_options.smooth_strength);
+        read(opt, "smooth_iterations", out_options.smooth_iterations);
+        read(opt, "smooth_skip_border", out_options.smooth_skip_border);
+        read(opt, "pipeline_v2", out_options.pipeline_v2);
+        read(opt, "v2_refine_mm", out_options.v2_refine_mm);
+        read(opt, "v2_regularize", out_options.v2_regularize);
+        read(opt, "v2_max_triangles_k", out_options.v2_max_triangles_k);
+        read(opt, "v2_relocate", out_options.v2_relocate);
+        read(opt, "v2_flip_edges", out_options.v2_flip_edges);
+        read(opt, "color_mix_enabled", out_options.color_mix_enabled);
+        read(opt, "color_despeckle", out_options.color_despeckle);
+        read(opt, "color_mix_count", out_options.color_mix_count);
+        read(opt, "active_slot", out_options.active_slot);
+        read(opt, "panel_mode", out_options.panel_mode);
+        out_options.active_slot = std::clamp(out_options.active_slot, 0, int(TEXTURE_DISPLACEMENT_MAX_LAYERS) - 1);
+        out_options.panel_mode  = std::clamp(out_options.panel_mode, 0, 1);
+    }
+
+    std::vector<TextureDisplacementLayer> out_layers;
+    // read() skips a value of the wrong type, but the vector, matrix, seam, island and UV-override arrays
+    // below read their numbers with get<>(), which throws on one; that rejects the document, like text that
+    // does not parse.
+    try {
+        if (const auto it = root.find("layers"); it != root.end() && it->is_array()) {
+            for (const nlohmann::json &j : *it) {
+                if (!j.is_object())
+                    continue;
+                TextureDisplacementLayer l;
+                read(j, "slot", l.slot);
+                // The panel and the paint masks are indexed by slot, so a layer without a valid one rejects the
+                // document rather than reaching them.
+                if (l.slot < 0 || l.slot >= int(TEXTURE_DISPLACEMENT_MAX_LAYERS))
+                    return false;
+                read(j, "name", l.name);
+                read(j, "path", l.path);
+                read(j, "path_in_3mf", l.path_in_3mf);
+
+                read(j, "depth_mm", l.depth_mm);
+                read(j, "tiling_scale", l.tiling_scale);
+                read(j, "rotation_deg", l.rotation_deg);
+                if (const auto o = j.find("offset"); o != j.end())
+                    l.offset = vec2_from_json(*o, l.offset);
+                read(j, "invert", l.invert);
+                read(j, "midlevel", l.midlevel);
+                read(j, "smoothing", l.smoothing);
+
+                read(j, "edge_smoothing", l.edge_smoothing);
+                read(j, "edge_smoothing_amount", l.edge_smoothing_amount);
+                read(j, "auto_connect_islands", l.auto_connect_islands);
+
+                read(j, "tile_enabled", l.tile_enabled);
+                read(j, "color_enabled", l.color_enabled);
+                int tile_method = int(l.tile_method), projection = int(l.projection_method), blend = int(l.blend_mode);
+                read_enum(j, "tile_method", tile_method);
+                read_enum(j, "projection_method", projection);
+                read_enum(j, "blend_mode", blend);
+                l.tile_method       = TextureTileMethod(tile_method);
+                l.projection_method = TextureProjectionMethod(std::clamp(projection, 0, 4));
+                l.blend_mode        = TextureBlendMode(blend);
+
+                read(j, "lscm_seam_angle_deg", l.lscm_seam_angle_deg);
+                read(j, "island_padding_mm", l.island_padding_mm);
+
+                if (const auto v = j.find("view_project_right"); v != j.end())
+                    l.view_project_right = vec3_from_json(*v, l.view_project_right);
+                if (const auto v = j.find("view_project_up"); v != j.end())
+                    l.view_project_up = vec3_from_json(*v, l.view_project_up);
+                read(j, "view_project_projective", l.view_project_projective);
+                if (const auto v = j.find("view_project_matrix"); v != j.end() && v->is_array() && v->size() == 12)
+                    for (size_t i = 0; i < 12; ++i)
+                        l.view_project_matrix[i] = (*v)[i].get<float>();
+
+                if (const auto v = j.find("lscm_seam_edges"); v != j.end() && v->is_array())
+                    for (size_t i = 0; i + 1 < v->size(); i += 2)
+                        l.lscm_seam_edges.emplace_back((*v)[i].get<int>(), (*v)[i + 1].get<int>());
+
+                if (const auto v = j.find("islands"); v != j.end() && v->is_array())
+                    for (const nlohmann::json &e : *v) {
+                        if (!e.is_array() || e.size() != 4)
+                            continue;
+                        TextureIsland island;
+                        island.offset       = Vec2f(e[0].get<float>(), e[1].get<float>());
+                        island.rotation_deg = e[2].get<float>();
+                        island.scale        = e[3].get<float>();
+                        l.islands.push_back(island);
+                    }
+
+                read(j, "island_groups", l.island_groups);
+
+                if (const auto v = j.find("lscm_uv_overrides"); v != j.end() && v->is_array())
+                    for (const nlohmann::json &e : *v) {
+                        if (!e.is_array() || e.size() != 3)
+                            continue;
+                        l.lscm_uv_overrides.emplace_back(e[0].get<int>(), Vec2f(e[1].get<float>(), e[2].get<float>()));
+                    }
+
+                out_layers.push_back(std::move(l));
+            }
+        }
+    } catch (const nlohmann::json::exception &) {
+        return false;
+    }
+
+    layers  = std::move(out_layers);
+    options = out_options;
+    return true;
+}

 } // namespace Slic3r
@@ -397,14 +397,41 @@ struct TextureDisplacementOptions
    // finer than the mesh leaves behind, without eating features that are genuinely a facet wide.
    int          color_despeckle   = 2;

+    // Where the panel was left, rather than anything the bake reads. It lives with the volume because
+    // that is what it describes: reopening a project should put the user back on the layer they were
+    // editing, in the mode they were editing it in, not on slot 0 in Standard.
+    int active_slot = 0;
+    int panel_mode  = 0; // 0 Standard, 1 Pro
+
    template<class Archive> void serialize(Archive &ar)
    {
        ar(displace_border, smooth_enabled, smooth_strength, smooth_iterations, smooth_skip_border,
           pipeline_v2, v2_refine_mm, v2_regularize, v2_max_triangles_k,
-           v2_relocate, color_mix_enabled, color_despeckle, color_mix_count);
+           v2_relocate, v2_flip_edges, color_mix_enabled, color_despeckle, color_mix_count,
+           active_slot, panel_mode);
    }
 };

+// Project persistence (see bbs_3mf.cpp). The layer stack and the per-volume options are written to the
+// .3mf as JSON rather than through the cereal save()/load() above: those two are positional and
+// unversioned, which is right for the undo/redo stack they serve (one session, one binary) but would
+// make every future field a project-breaking change. A JSON object tolerates both directions - an
+// unknown key is ignored, a missing one keeps the member's default - so old projects keep loading and
+// new ones degrade gracefully in older builds.
+//
+// The texture image itself is *not* in here. It is a binary blob that belongs in the archive as a file
+// of its own, exactly as EmbossShape stores its SVG; `path_in_3mf` names that file, and the caller is
+// responsible for writing it and for filling `image_data` back in on load.
+std::string texture_displacement_layers_to_json(const std::vector<TextureDisplacementLayer> &layers,
+                                                const TextureDisplacementOptions            &options);
+// Returns false and leaves both outputs untouched when the text is not a valid JSON object, a number in a
+// layer's vector, matrix, seam, island or UV-override array has the wrong type, or a layer's slot is
+// missing or outside [0, TEXTURE_DISPLACEMENT_MAX_LAYERS). Any other value of the wrong type or shape
+// keeps its default.
+bool texture_displacement_layers_from_json(const std::string                      &text,
+                                           std::vector<TextureDisplacementLayer>  &layers,
+                                           TextureDisplacementOptions             &options);
+
 // How much detail a height texture carries: central differences of the grey image, the mean gradient
 // and the share of texels steeper than 30 grey levels, mapped to how many texels one mesh edge may
 // span (1 for a hard-edged image, 4 for a smooth one). Cached per image, like the decode.
@@ -3558,6 +3558,7 @@ const ModelVolume* GLGizmoTextureDisplacement::texture_volume() const

 void GLGizmoTextureDisplacement::update_model_object()
 {
+    store_panel_state();
    bool         updated = false;
    ModelObject *mo      = m_c->selection_info()->model_object();
    int          idx     = -1;
@@ -3593,6 +3594,24 @@ void GLGizmoTextureDisplacement::update_from_model_object(bool first_update)
 {
    wxBusyCursor wait;

+    // Opening the gizmo puts the panel back where it was left: the layer and the mode come off the
+    // volume, because they are the user's place in this model's stack, and the dock state off the
+    // application config, because it is about their window. Only on open - this also runs on an
+    // undo/redo and on a layer switch, where overriding what the user is doing now would be wrong.
+    if (first_update) {
+        if (const ModelVolume *mv = texture_volume(); mv != nullptr) {
+            const TextureDisplacementOptions &opts = mv->texture_displacement_options;
+            m_panel_mode = std::clamp(opts.panel_mode, 0, 1);
+            // Only if that slot still holds a layer: the stack can have been edited by anything that
+            // does not go through the panel, and a selection pointing at nothing shows an empty panel.
+            const auto &stack = mv->texture_displacement_layers;
+            if (std::any_of(stack.begin(), stack.end(),
+                            [&opts](const TextureDisplacementLayer &l) { return l.slot == opts.active_slot; }))
+                m_active_layer_slot = opts.active_slot;
+        }
+        m_undocked = wxGetApp().app_config->get_bool(UNDOCKED_CONFIG_KEY);
+    }
+
    const ModelObject *mo = m_c->selection_info()->model_object();
    m_triangle_selectors.clear();
    // The base keeps the last mesh a fill tool hovered, and render_painter_gizmo() reads it as a hover that is
@@ -3641,6 +3660,14 @@ void GLGizmoTextureDisplacement::update_from_model_object(bool first_update)
    rebuild_preview();
 }

+void GLGizmoTextureDisplacement::store_panel_state()
+{
+    if (ModelVolume *mv = texture_volume(); mv != nullptr) {
+        mv->texture_displacement_options.active_slot = m_active_layer_slot;
+        mv->texture_displacement_options.panel_mode  = m_panel_mode;
+    }
+}
+
 void GLGizmoTextureDisplacement::set_active_layer(int slot)
 {
    if (slot == m_active_layer_slot)
@@ -3649,6 +3676,7 @@ void GLGizmoTextureDisplacement::set_active_layer(int slot)
    // reflect - otherwise they would be silently lost.
    update_model_object();
    m_active_layer_slot = slot;
+    store_panel_state();
    update_from_model_object(false);
    // The on-canvas gizmo (if on) is anchored to whichever layer is active - keep it in sync
    // instead of leaving it pointing at the previous layer's (now stale) paint patch.
@@ -5986,6 +6014,7 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
                                   "not what you wanted and you know why."));
            if (clicked && !on) {
                m_panel_mode = m;
+                store_panel_state();
                if (!pro_mode()) {
                    // Leaving the subdivision preview open would strand a wireframe whose controls just
                    // disappeared, so close it as part of the switch.
@@ -6008,6 +6037,7 @@ void GLGizmoTextureDisplacement::on_render_input_window(float x, float y, float
                        _L("Detach this panel so it can be dragged anywhere over the 3D view, or dock it back beside "
                           "the toolbar.")))
            m_undocked = !m_undocked;
+            wxGetApp().app_config->set_bool(UNDOCKED_CONFIG_KEY, m_undocked);
    }
    ImGui::Separator();

@@ -262,6 +262,9 @@ private:
    // Standard is active so what Preview shows is always what Bake will do. Returns true if it actually
    // changed something, so the caller can invalidate the preview.
    bool apply_standard_mode_presets(ModelVolume *mv);
+    // Copies the panel's own state (active layer, Standard/Pro) onto the volume, so the project file
+    // can carry it. Cheap and idempotent - called wherever either of the two changes.
+    void store_panel_state();
    // Standard mode's Bake: remesh to an even density, refine where the texture bends, then displace.
    // The order matters and is the whole reason this is one button - a height map can only move
    // existing vertices, so the mesh has to be prepared first, and remeshing after painting would drop
@@ -971,9 +974,12 @@ private:
    PatchUnwrap m_uv_editor_unwrap;

    // When set, the panel is a free-floating window the user can drag anywhere (with a title bar to
-    // grab), instead of being pinned to the right of the gizmo toolbar. Persisted across gizmo
-    // open/close within a session, so the choice sticks while working.
+    // grab), instead of being pinned to the right of the gizmo toolbar. Kept in the application
+    // config rather than in the project: it describes the user's window, not the model, so opening
+    // someone else's project must not move their panel.
    bool m_undocked = false;
+    // The config key behind m_undocked.
+    static constexpr const char *UNDOCKED_CONFIG_KEY = "texture_displacement_panel_undocked";

    // Smooth scrolling for the panel body (everything between the header and the pinned Bake footer).
    // ImGui jumps a fixed number of lines per wheel notch, which on tall layer cards reads as a hard
@@ -28,6 +28,7 @@
 #include <miniz.h>
 #include "libslic3r/TriangleMesh.hpp"
 #include "libslic3r/TriangleSelector.hpp"
+#include "libslic3r/TextureDisplacement.hpp"
 #include <memory>
 #include <cstdint>
 #include <ios>
@@ -38,6 +39,7 @@
 #include <boost/algorithm/string/predicate.hpp>
 #include <algorithm>
 #include <functional>
+#include <initializer_list>

 #include <catch2/catch_tostring.hpp>
 #include <Eigen/Core>
@@ -349,6 +351,24 @@ static bool replace_in_3mf_entry(const std::string& path, const std::string& suf
    return replaced;
 }

+// Stores `model` as a one-plate project.
+static void store_project(Model& model, const std::string& path, SaveStrategy strategy)
+{
+    ScopedTemporaryDir backup_dir("orca_paint_src");
+    model.set_backup_path(backup_dir.string());
+
+    DynamicPrintConfig cfg;
+    PlateData          plate;
+    plate.plate_index = 0;
+    StoreParams sp;
+    sp.path     = path.c_str();
+    sp.model    = &model;
+    sp.config   = &cfg;
+    sp.strategy = strategy;
+    sp.plate_data_list.push_back(&plate);
+    REQUIRE(store_bbs_3mf(sp));
+}
+
 // Stores a one-plate project holding a cube whose first two facets are painted Extruder2 and
 // Extruder3, which the exporter writes as paint_color="8" and paint_color="0C".
 static void store_painted_cube(const std::string& path)
@@ -363,19 +383,7 @@ static void store_painted_cube(const std::string& path)
        selector.set_facet(1, EnforcerBlockerType::Extruder3);
        REQUIRE(volume->mmu_segmentation_facets.set(selector));
    }
-    ScopedTemporaryDir backup_dir("orca_paint_src");
-    model.set_backup_path(backup_dir.string());
-
-    DynamicPrintConfig cfg;
-    PlateData          plate;
-    plate.plate_index = 0;
-    StoreParams sp;
-    sp.path     = path.c_str();
-    sp.model    = &model;
-    sp.config   = &cfg;
-    sp.strategy = SaveStrategy::Zip64 | SaveStrategy::Silence;
-    sp.plate_data_list.push_back(&plate);
-    REQUIRE(store_bbs_3mf(sp));
+    store_project(model, path, SaveStrategy::Zip64 | SaveStrategy::Silence);
 }

 // Loads `path` through the BBS importer into `model`, releasing the plates it returns. The
@@ -501,6 +509,163 @@ TEST_CASE("A project with malformed paint data loads without the damaged facet",
    REQUIRE(selector.num_facets(EnforcerBlockerType::Extruder3) == 1);
 }

+// Paints `triangles` of `volume` on texture displacement layer slot `slot`.
+static void paint_texture_slot(ModelVolume& volume, int slot, std::initializer_list<int> triangles)
+{
+    TriangleSelector selector(volume.mesh());
+    for (const int triangle : triangles)
+        selector.set_facet(triangle, EnforcerBlockerType::ENFORCER);
+    REQUIRE(volume.texture_displacement_facet(slot).set(selector));
+}
+
+// Every triangle's texture paint on every slot, in the form the exporter writes it, so two volumes
+// compare equal only when the same triangles are painted on the same slots.
+static std::vector<std::string> texture_paint(const ModelVolume& volume)
+{
+    std::vector<std::string> paint;
+    for (int slot = 0; slot < int(TEXTURE_DISPLACEMENT_MAX_LAYERS); ++slot)
+        for (size_t i = 0; i < volume.mesh().its.indices.size(); ++i)
+            paint.push_back(volume.texture_displacement_facet(slot).get_triangle_as_string(int(i)));
+    return paint;
+}
+
+// A cube with one texture displacement layer in slot 2 and texture paint on gapped triangles of two
+// slots. The layer's image bytes need not decode: the archive stores them as they are.
+static ModelVolume& add_texture_displaced_cube(Model& model)
+{
+    ModelObject* object = model.add_object();
+    ModelVolume* volume = object->add_volume(make_cube(10., 10., 10.));
+    object->add_instance();
+
+    TextureDisplacementLayer layer;
+    layer.slot       = 2;
+    layer.name       = "Bark";
+    layer.depth_mm   = 1.25f;
+    layer.image_data = std::make_shared<std::vector<unsigned char>>(std::vector<unsigned char>{ 0x89, 'P', 'N', 'G', 1, 2, 3 });
+    volume->texture_displacement_layers.push_back(layer);
+    volume->texture_displacement_options.active_slot = 2;
+
+    paint_texture_slot(*volume, 2, { 3, 7 });
+    paint_texture_slot(*volume, 5, { 10 });
+    return *volume;
+}
+
+TEST_CASE("Texture displacement layers, textures and paint survive a project round trip", "[3mf]")
+{
+    // A single model file, and one file per object (read by a separate importer).
+    const SaveStrategy strategy = GENERATE(SaveStrategy::Zip64 | SaveStrategy::Silence,
+                                           SaveStrategy::Zip64 | SaveStrategy::Silence | SaveStrategy::SplitModel);
+    INFO("save strategy " << int(strategy));
+
+    ScopedTemporaryFile temp(".3mf");
+    Model               source;
+    const ModelVolume&  painted = add_texture_displaced_cube(source);
+    const std::vector<std::string> paint = texture_paint(painted);
+    REQUIRE(std::count_if(paint.begin(), paint.end(), [](const std::string& s) { return !s.empty(); }) == 3);
+    store_project(source, temp.string(), strategy);
+
+    ScopedTemporaryDir backup_dir("orca_texdisp_dst");
+    Model              model;
+    REQUIRE(load_project(temp.string(), model, backup_dir));
+    REQUIRE(model.objects.size() == 1);
+    const ModelVolume& volume = *model.objects.front()->volumes.front();
+
+    REQUIRE(volume.texture_displacement_layers.size() == 1);
+    const TextureDisplacementLayer& layer = volume.texture_displacement_layers.front();
+    CHECK(layer.slot == 2);
+    CHECK(layer.name == "Bark");
+    CHECK_THAT(layer.depth_mm, Catch::Matchers::WithinAbs(1.25f, 1e-6f));
+    REQUIRE(layer.image_data);
+    CHECK(*layer.image_data == *painted.texture_displacement_layers.front().image_data);
+    CHECK(volume.texture_displacement_options.active_slot == 2);
+    CHECK(texture_paint(volume) == paint);
+}
+
+TEST_CASE("Volumes sharing a mesh keep their own texture displacement paint", "[3mf]")
+{
+    Model        source;
+    ModelObject* first_object = source.add_object();
+    ModelVolume* first        = first_object->add_volume(make_cube(10., 10., 10.));
+    first_object->add_instance();
+    ModelVolume* second = source.add_object(*first_object)->volumes.front();
+    REQUIRE(second->mesh_ptr() == first->mesh_ptr());
+    paint_texture_slot(*first, 0, { 3 });
+    paint_texture_slot(*second, 0, { 7 });
+
+    // What a project save from the app uses: one file per object, an identical mesh written once.
+    ScopedTemporaryFile temp(".3mf");
+    store_project(source, temp.string(),
+                  SaveStrategy::Zip64 | SaveStrategy::Silence | SaveStrategy::SplitModel | SaveStrategy::ShareMesh);
+
+    ScopedTemporaryDir backup_dir("orca_texdisp_dst");
+    Model              model;
+    REQUIRE(load_project(temp.string(), model, backup_dir));
+    REQUIRE(model.objects.size() == 2);
+    CHECK(texture_paint(*model.objects[0]->volumes.front()) == texture_paint(*first));
+    CHECK(texture_paint(*model.objects[1]->volumes.front()) == texture_paint(*second));
+}
+
+TEST_CASE("A texture displacement layer never loads its image from outside the project", "[3mf]")
+{
+    // A file the layer names, on the machine opening the project, that the project did not carry.
+    ScopedTemporaryFile texture(".png");
+    {
+        boost::nowide::ofstream file(texture.string(), std::ios::binary);
+        file << "not part of the project";
+    }
+    REQUIRE(boost::filesystem::file_size(texture.path()) > 0);
+
+    Model        source;
+    ModelObject* object = source.add_object();
+    ModelVolume* volume = object->add_volume(make_cube(10., 10., 10.));
+    object->add_instance();
+    TextureDisplacementLayer layer;
+    layer.slot     = 0;
+    layer.name     = "Elsewhere";
+    layer.path     = texture.string();
+    layer.depth_mm = 0.75f;
+    volume->texture_displacement_layers.push_back(layer);
+
+    ScopedTemporaryFile temp(".3mf");
+    store_project(source, temp.string(), SaveStrategy::Zip64 | SaveStrategy::Silence);
+
+    ScopedTemporaryDir backup_dir("orca_texdisp_dst");
+    Model              model;
+    REQUIRE(load_project(temp.string(), model, backup_dir));
+    REQUIRE(model.objects.size() == 1);
+    const std::vector<TextureDisplacementLayer>& layers = model.objects.front()->volumes.front()->texture_displacement_layers;
+    REQUIRE(layers.size() == 1);
+    CHECK(layers.front().name == "Elsewhere");
+    CHECK_THAT(layers.front().depth_mm, Catch::Matchers::WithinAbs(0.75f, 1e-6f));
+    CHECK_FALSE(layers.front().image_data);
+}
+
+TEST_CASE("A project with a malformed texture displacement value still loads", "[3mf][Regression]")
+{
+    const auto [from, to] = GENERATE(table<std::string, std::string>({
+        { "\"islands\":[]", "\"islands\":[[null,0,0,1]]" }, // a number that is null
+        { "\"slot\":2", "\"slot\":8" },                     // a slot past the last
+    }));
+    INFO(from << " -> " << to);
+
+    ScopedTemporaryFile temp(".3mf");
+    Model               source;
+    const ModelVolume&  painted = add_texture_displaced_cube(source);
+    store_project(source, temp.string(), SaveStrategy::Zip64 | SaveStrategy::Silence);
+    REQUIRE(replace_in_3mf_entry(temp.string(), ".json", from, to));
+
+    ScopedTemporaryDir backup_dir("orca_texdisp_dst");
+    Model              model;
+    bool               loaded = false;
+    REQUIRE_NOTHROW(loaded = load_project(temp.string(), model, backup_dir));
+    REQUIRE(loaded);
+    REQUIRE(model.objects.size() == 1);
+    const ModelVolume& volume = *model.objects.front()->volumes.front();
+    // The layer stack is dropped as a whole; the paint, stored apart from it, still loads.
+    CHECK(volume.texture_displacement_layers.empty());
+    CHECK(texture_paint(volume) == texture_paint(painted));
+}
+
 // The recipe lives only in the BBS-native backend, because that is the only one that runs:
 // store_bbs_3mf is the sole exporter the app calls, and 3mf.cpp's load_3mf is reached only for
 // files fingerprinted as PrusaSlicer's, which never carry a recipe. This locks in both halves:
@@ -32,6 +32,7 @@
 #include <fstream>
 #include <limits>
 #include <set>
+#include <string>
 #include <boost/filesystem.hpp>

 #include "libslic3r/AABBMesh.hpp"
@@ -2157,6 +2158,177 @@ TEST_CASE("A second bake beside a first comes out as fine as a single bake", "[T
    CHECK(second <= single * 5 / 4);
 }

+// The .3mf stores the layer stack as JSON (see texture_displacement_layers_to_json). Two properties
+// matter: everything the UV editor and the panel can set has to survive a round trip, and a document
+// written by a build that knew fewer fields has to keep loading, with the missing ones left at their
+// defaults rather than zeroed.
+TEST_CASE("Texture displacement layers survive a JSON round trip", "[TextureDisplacement]")
+{
+    std::vector<TextureDisplacementLayer> layers(2);
+    TextureDisplacementLayer             &a = layers[0];
+    a.slot                 = 0;
+    a.name                 = "Bark";
+    a.path                 = "/textures/bark.png";
+    a.depth_mm             = 1.25f;
+    a.tiling_scale         = 7.5f;
+    a.rotation_deg         = 30.f;
+    a.offset               = Vec2f(0.25f, -0.5f);
+    a.invert               = true;
+    a.midlevel             = 0.125f;
+    a.smoothing            = 0.75f;
+    a.edge_smoothing       = true;
+    a.edge_smoothing_amount = 0.25f;
+    a.auto_connect_islands = false;
+    a.tile_enabled         = false;
+    a.tile_method          = TextureTileMethod::MirroredRepeat;
+    a.projection_method    = TextureProjectionMethod::LSCM;
+    a.blend_mode           = TextureBlendMode::Subtract;
+    a.color_enabled        = true;
+    a.lscm_seam_angle_deg  = 45.f;
+    a.island_padding_mm    = 0.5f;
+    a.lscm_seam_edges      = { { 1, 2 }, { 3, 5 } };
+    a.islands              = { TextureIsland{ Vec2f(1.f, 2.f), 15.f, 1.5f }, TextureIsland{} };
+    a.island_groups        = { 0, 0 };
+    a.lscm_uv_overrides    = { { -4, Vec2f(0.5f, 0.75f) } };
+
+    TextureDisplacementLayer &b = layers[1];
+    b.slot                    = 1;
+    b.projection_method       = TextureProjectionMethod::ViewProjected;
+    b.view_project_right      = Vec3f(0.f, 1.f, 0.f);
+    b.view_project_up         = Vec3f(0.f, 0.f, 1.f);
+    b.view_project_projective = true;
+    for (size_t i = 0; i < b.view_project_matrix.size(); ++i)
+        b.view_project_matrix[i] = float(i) + 0.5f;
+
+    TextureDisplacementOptions options;
+    options.displace_border   = false;
+    options.smooth_enabled    = true;
+    options.smooth_strength   = 0.6f;
+    options.smooth_iterations = 5;
+    options.pipeline_v2       = false;
+    options.v2_max_triangles_k = 250;
+    options.color_mix_count   = 3;
+    options.color_despeckle   = 4;
+    options.active_slot       = 3;
+    options.panel_mode        = 1;
+
+    const std::string json = texture_displacement_layers_to_json(layers, options);
+
+    std::vector<TextureDisplacementLayer> read_layers;
+    TextureDisplacementOptions            read_options;
+    REQUIRE(texture_displacement_layers_from_json(json, read_layers, read_options));
+    REQUIRE(read_layers.size() == layers.size());
+
+    const TextureDisplacementLayer &ra = read_layers[0];
+    CHECK(ra.name == a.name);
+    CHECK(ra.path == a.path);
+    CHECK_THAT(ra.depth_mm, WithinAbs(a.depth_mm, 1e-6f));
+    CHECK_THAT(ra.tiling_scale, WithinAbs(a.tiling_scale, 1e-6f));
+    CHECK_THAT(ra.rotation_deg, WithinAbs(a.rotation_deg, 1e-6f));
+    CHECK(ra.offset.isApprox(a.offset));
+    CHECK(ra.invert == a.invert);
+    CHECK_THAT(ra.midlevel, WithinAbs(a.midlevel, 1e-6f));
+    CHECK_THAT(ra.smoothing, WithinAbs(a.smoothing, 1e-6f));
+    CHECK(ra.edge_smoothing == a.edge_smoothing);
+    CHECK_THAT(ra.edge_smoothing_amount, WithinAbs(a.edge_smoothing_amount, 1e-6f));
+    CHECK(ra.auto_connect_islands == a.auto_connect_islands);
+    CHECK(ra.tile_enabled == a.tile_enabled);
+    CHECK(ra.tile_method == a.tile_method);
+    CHECK(ra.projection_method == a.projection_method);
+    CHECK(ra.blend_mode == a.blend_mode);
+    CHECK(ra.color_enabled == a.color_enabled);
+    CHECK_THAT(ra.lscm_seam_angle_deg, WithinAbs(a.lscm_seam_angle_deg, 1e-6f));
+    CHECK_THAT(ra.island_padding_mm, WithinAbs(a.island_padding_mm, 1e-6f));
+    CHECK(ra.lscm_seam_edges == a.lscm_seam_edges);
+    REQUIRE(ra.islands.size() == a.islands.size());
+    CHECK(ra.islands[0].offset.isApprox(a.islands[0].offset));
+    CHECK_THAT(ra.islands[0].rotation_deg, WithinAbs(a.islands[0].rotation_deg, 1e-6f));
+    CHECK_THAT(ra.islands[0].scale, WithinAbs(a.islands[0].scale, 1e-6f));
+    CHECK(ra.island_groups == a.island_groups);
+    REQUIRE(ra.lscm_uv_overrides.size() == 1);
+    CHECK(ra.lscm_uv_overrides[0].first == -4);
+    CHECK(ra.lscm_uv_overrides[0].second.isApprox(Vec2f(0.5f, 0.75f)));
+
+    const TextureDisplacementLayer &rb = read_layers[1];
+    CHECK(rb.projection_method == TextureProjectionMethod::ViewProjected);
+    CHECK(rb.view_project_right.isApprox(b.view_project_right));
+    CHECK(rb.view_project_up.isApprox(b.view_project_up));
+    CHECK(rb.view_project_projective);
+    CHECK(rb.view_project_matrix == b.view_project_matrix);
+
+    CHECK(read_options.displace_border == options.displace_border);
+    CHECK(read_options.smooth_enabled == options.smooth_enabled);
+    CHECK_THAT(read_options.smooth_strength, WithinAbs(options.smooth_strength, 1e-6f));
+    CHECK(read_options.smooth_iterations == options.smooth_iterations);
+    CHECK(read_options.pipeline_v2 == options.pipeline_v2);
+    CHECK(read_options.v2_max_triangles_k == options.v2_max_triangles_k);
+    CHECK(read_options.color_mix_count == options.color_mix_count);
+    CHECK(read_options.color_despeckle == options.color_despeckle);
+    // Where the panel was left comes back with the rest, so a reopened project is on the same layer.
+    CHECK(read_options.active_slot == options.active_slot);
+    CHECK(read_options.panel_mode == options.panel_mode);
+}
+
+TEST_CASE("Texture displacement JSON keeps defaults for keys it does not carry", "[TextureDisplacement]")
+{
+    // What a build that knew fewer fields would have written: one layer, almost nothing set.
+    const std::string sparse = R"({"version":1,"layers":[{"slot":2,"name":"Old","depth_mm":0.75}]})";
+
+    std::vector<TextureDisplacementLayer> layers;
+    TextureDisplacementOptions            options;
+    REQUIRE(texture_displacement_layers_from_json(sparse, layers, options));
+    REQUIRE(layers.size() == 1);
+
+    const TextureDisplacementLayer  &l = layers[0];
+    const TextureDisplacementLayer   fresh;
+    const TextureDisplacementOptions defaults;
+    CHECK(l.slot == 2);
+    CHECK(l.name == "Old");
+    CHECK_THAT(l.depth_mm, WithinAbs(0.75f, 1e-6f));
+    // Everything absent keeps the struct's own default rather than becoming zero.
+    CHECK_THAT(l.tiling_scale, WithinAbs(fresh.tiling_scale, 1e-6f));
+    CHECK(l.auto_connect_islands == fresh.auto_connect_islands);
+    CHECK(l.tile_enabled == fresh.tile_enabled);
+    CHECK(l.projection_method == fresh.projection_method);
+    CHECK_THAT(l.lscm_seam_angle_deg, WithinAbs(fresh.lscm_seam_angle_deg, 1e-6f));
+    CHECK(options.color_mix_count == defaults.color_mix_count);
+    CHECK(options.pipeline_v2 == defaults.pipeline_v2);
+    CHECK(options.active_slot == defaults.active_slot);
+    CHECK(options.panel_mode == defaults.panel_mode);
+
+    std::vector<TextureDisplacementLayer> unused_layers;
+    TextureDisplacementOptions            unused_options;
+    CHECK(!texture_displacement_layers_from_json("not json at all", unused_layers, unused_options));
+}
+
+TEST_CASE("Texture displacement JSON with a wrong-typed element or an out-of-range slot is rejected", "[TextureDisplacement]")
+{
+    const std::string layer = GENERATE(as<std::string>{},
+                                       R"({"slot":0,"offset":["x",0]})",
+                                       R"({"slot":0,"view_project_right":[null,0,0]})",
+                                       R"({"slot":0,"view_project_matrix":[0,0,0,0,0,0,0,0,0,0,0,"x"]})",
+                                       R"({"slot":0,"lscm_seam_edges":[1,null]})",
+                                       R"({"slot":0,"islands":[[0,0,"x",1]]})",
+                                       R"({"slot":0,"lscm_uv_overrides":[[null,0,0]]})",
+                                       R"({"slot":8})",
+                                       R"({"slot":-1})",
+                                       R"({"slot":"x"})",
+                                       R"({"name":"No slot"})");
+    INFO(layer);
+
+    std::vector<TextureDisplacementLayer> layers(1);
+    layers.front().name = "Kept";
+    TextureDisplacementOptions options;
+    options.color_mix_count = 7;
+
+    bool parsed = true;
+    REQUIRE_NOTHROW(parsed = texture_displacement_layers_from_json(R"({"version":1,"layers":[)" + layer + "]}", layers, options));
+    CHECK_FALSE(parsed);
+    REQUIRE(layers.size() == 1);
+    CHECK(layers.front().name == "Kept");
+    CHECK(options.color_mix_count == 7);
+}
+
 TEST_CASE("whether a layer's texture has colour agrees with its decode", "[TextureDisplacement]")
 {
    TextureDisplacementLayer gray;