Add Linux ARM64 (aarch64) AppImage build

Build the Linux AppImage for ARM64 (aarch64) alongside x86_64: the Linux CI
job now matrixes over both architectures, with arch-aware deps caching and
artifact/asset names (amd64 keeps its existing names). The aarch64 AppImage is
published to the nightly and release pages like the x86_64 one.

Run the unit-test suite on the aarch64 runner (faster GitHub arm runner); the
tests are built on that leg. Self-hosted keeps tests on the amd64 server.

.github/workflows/build_all.yml

@@ -55,11 +55,23 @@ jobs:
   build_linux:
     strategy:
       fail-fast: false
+      # Build both arches on every event (PRs included), through the same
+      # build_check_cache -> build_deps -> build_orca chain (the AppImage).
+      # aarch64 always uses the GitHub-hosted arm runner (there is no arm
+      # self-hosted server). amd64's empty arch is load-bearing: it keeps the
+      # historical 'linux-clang' deps cache key and the unsuffixed asset names.
+      matrix:
+        include:
+          - arch: ""
+            os: ${{ vars.SELF_HOSTED && 'orca-lnx-server' || 'ubuntu-24.04' }}
+          - arch: "aarch64"
+            os: ubuntu-24.04-arm
     # Don't run scheduled builds on forks:
     if: ${{ !cancelled() && (github.event_name != 'schedule' || github.repository == 'OrcaSlicer/OrcaSlicer') }}
     uses: ./.github/workflows/build_check_cache.yml
     with:
-      os: ${{ vars.SELF_HOSTED && 'orca-lnx-server' || 'ubuntu-24.04' }}
+      os: ${{ matrix.os }}
+      arch: ${{ matrix.arch }}
       build-deps-only: ${{ inputs.build-deps-only || false }}
     secrets: inherit
   build_windows:
@@ -99,7 +111,9 @@ jobs:
     secrets: inherit
   unit_tests:
     name: Unit Tests
-    runs-on: ${{ vars.SELF_HOSTED && 'orca-lnx-server' || 'ubuntu-24.04' }}
+    # Tests are built on the aarch64 leg by default (faster GitHub arm runner),
+    # so run them there; self-hosted builds them on the amd64 server instead.
+    runs-on: ${{ vars.SELF_HOSTED && 'orca-lnx-server' || 'ubuntu-24.04-arm' }}
     needs: build_linux
     if: ${{ !cancelled() && success() }}
     steps:
@@ -237,4 +251,3 @@ jobs:
         asset_name: OrcaSlicer-Linux-flatpak_nightly_${{ matrix.variant.arch }}.flatpak
         asset_content_type: application/octet-stream
         max_releases: 1 # optional, if there are more releases than this matching the asset_name, the oldest ones are going to be deleted
-

.github/workflows/build_check_cache.yml

@@ -33,8 +33,10 @@ jobs:
       - name: set outputs
         id: set_outputs
         env:
-          # Keep macOS cache keys and paths architecture-specific.
+          # Keep macOS/Linux cache keys architecture-specific. amd64 Linux passes
-          cache-os: ${{ runner.os == 'macOS' && format('macos-{0}', inputs.arch) || (runner.os == 'Windows' && 'windows' || 'linux-clang') }}
+          # no arch (key stays 'linux-clang', preserving the existing cache);
+          # aarch64 gets its own 'linux-clang-aarch64' key.
+          cache-os: ${{ runner.os == 'macOS' && format('macos-{0}', inputs.arch) || (runner.os == 'Windows' && 'windows' || format('linux-clang{0}', inputs.arch && format('-{0}', inputs.arch) || '')) }}
           dep-folder-name: ${{ runner.os == 'macOS' && format('/{0}', inputs.arch) || '/OrcaSlicer_dep' }}
           output-cmd: ${{ runner.os == 'Windows' && '$env:GITHUB_OUTPUT' || '"$GITHUB_OUTPUT"'}}
         run: |

.github/workflows/build_orca.yml

@@ -65,6 +65,11 @@ jobs:
           echo "ver_pure=$ver_pure" >> $GITHUB_ENV
           echo "date=$(date +'%Y%m%d')" >> $GITHUB_ENV
           echo "git_commit_hash=$git_commit_hash" >> $GITHUB_ENV
+          # Per-arch Linux AppImage naming: amd64 keeps the historical unsuffixed
+          # name (arch_suffix empty). Unused on macOS/Windows.
+          if [ '${{ inputs.arch }}' = 'aarch64' ]; then
+            echo "arch_suffix=_aarch64" >> $GITHUB_ENV
+          fi
         shell: bash
 
       - name: Get the version and date on Windows
@@ -401,16 +406,23 @@ jobs:
         if: runner.os == 'Linux'
         shell: bash
         run: |
-          ./build_linux.sh -istrlL
+          # Build + tar the unit tests (-t) only on the leg that runs them: the
+          # aarch64 leg by default (faster GitHub arm runner), or amd64 when using
+          # self-hosted runners (no arm self-hosted server). unit_tests downloads
+          # this tarball. The profile validator is built with -s, so amd64 keeps it.
+          tests=${{ (!vars.SELF_HOSTED && inputs.arch == 'aarch64') || (vars.SELF_HOSTED && inputs.arch != 'aarch64') }}
+          if $tests; then flags=-istrlL; else flags=-isrlL; fi
+          ./build_linux.sh "$flags"
           ./scripts/check_appimage_libs.sh ./build/package ./build/package/bin/orca-slicer
-          mv -n ./build/OrcaSlicer_Linux_V${{ env.ver_pure }}.AppImage ./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}_${{ env.ver }}.AppImage
+          appimage=./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}${{ env.arch_suffix }}_${{ env.ver }}.AppImage
-          chmod +x ./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}_${{ env.ver }}.AppImage
+          mv -n ./build/OrcaSlicer_Linux_V${{ env.ver_pure }}.AppImage "$appimage"
-          tar -cvpf build_tests.tar build/tests
+          chmod +x "$appimage"
+          if $tests; then tar -cvpf build_tests.tar build/tests; fi
 
         # Use tar because upload-artifacts won't always preserve directory structure
         # and doesn't preserve file permissions
       - name: Upload Test Artifact
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && ((!vars.SELF_HOSTED && inputs.arch == 'aarch64') || (vars.SELF_HOSTED && inputs.arch != 'aarch64'))
         uses: actions/upload-artifact@v7
         with:
           name: ${{ github.sha }}-tests
@@ -420,7 +432,7 @@ jobs:
           if-no-files-found: error
 
       - name: Run external slicer regression tests
-        if: runner.os == 'Linux'
+        if: runner.os == 'Linux' && inputs.arch != 'aarch64'
         timeout-minutes: 20
         shell: bash
         run: |
@@ -430,7 +442,7 @@ jobs:
           python3 "$test_repo_dir/run_test.py" "${{ github.workspace }}/build/package/bin/orca-slicer"
 
       - name: Build orca_custom_preset_tests
-        if: github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED
+        if: github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED && inputs.arch != 'aarch64'
         working-directory: ${{ github.workspace }}/build/src/Release
         shell: bash
         run: |
@@ -442,11 +454,11 @@ jobs:
         if: ${{ ! env.ACT && runner.os == 'Linux' }}
         uses: actions/upload-artifact@v7
         with:
-          name: OrcaSlicer_Linux_ubuntu_${{ env.ubuntu-ver }}_${{ env.ver }}
+          name: OrcaSlicer_Linux_ubuntu_${{ env.ubuntu-ver }}${{ env.arch_suffix }}_${{ env.ver }}
-          path: './build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}_${{ env.ver }}.AppImage'
+          path: "./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}${{ env.arch_suffix }}_${{ env.ver }}.AppImage"
 
       - name: Upload OrcaSlicer_profile_validator Ubuntu
-        if: ${{ ! env.ACT && runner.os == 'Linux' && !vars.SELF_HOSTED }}
+        if: ${{ ! env.ACT && runner.os == 'Linux' && !vars.SELF_HOSTED && inputs.arch != 'aarch64' }}
         uses: actions/upload-artifact@v7
         with:
           name: OrcaSlicer_profile_validator_Linux_ubuntu_${{ env.ubuntu-ver }}_${{ env.ver }}
@@ -458,12 +470,12 @@ jobs:
         with:
           upload_url: https://uploads.github.com/repos/OrcaSlicer/OrcaSlicer/releases/137995723/assets{?name,label}
           release_id: 137995723
-          asset_path: ./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}_${{ env.ver }}.AppImage
+          asset_path: ./build/OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}${{ env.arch_suffix }}_${{ env.ver }}.AppImage
-          asset_name: OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}_nightly.AppImage
+          asset_name: OrcaSlicer_Linux_AppImage${{ env.ubuntu-ver-str }}${{ env.arch_suffix }}_nightly.AppImage
           asset_content_type: application/octet-stream
           max_releases: 1 # optional, if there are more releases than this matching the asset_name, the oldest ones are going to be deleted
       - name: Deploy Ubuntu release
-        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED }}
+        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED && inputs.arch != 'aarch64' }}
         uses: rickstaa/action-create-tag@v1
         with:
           tag: "nightly-builds"
@@ -472,7 +484,7 @@ jobs:
           message: "nightly-builds"
 
       - name: Deploy Ubuntu OrcaSlicer_profile_validator release
-        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED }}
+        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED && inputs.arch != 'aarch64' }}
         uses: WebFreak001/deploy-nightly@v3.2.0
         with:
           upload_url: https://uploads.github.com/repos/OrcaSlicer/OrcaSlicer/releases/137995723/assets{?name,label}
@@ -483,7 +495,7 @@ jobs:
           max_releases: 1
 
       - name: Deploy orca_custom_preset_tests
-        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED }}
+        if: ${{ github.repository == 'OrcaSlicer/OrcaSlicer' && ! env.ACT && github.ref == 'refs/heads/main' && runner.os == 'Linux' && !vars.SELF_HOSTED && inputs.arch != 'aarch64' }}
         uses: WebFreak001/deploy-nightly@v3.2.0
         with:
           upload_url: https://uploads.github.com/repos/OrcaSlicer/OrcaSlicer/releases/137995723/assets{?name,label}

.github/workflows/publish_release.yml

@@ -17,7 +17,7 @@ on:
         required: true
         type: string
       tag:
-        description: 'Tag of the draft release to upload to (e.g. v2.4.0-beta)'
+        description: 'Tag of the draft release to upload to (e.g. v2.4.0)'
         required: true
         type: string
 

README.md

@@ -161,6 +161,8 @@ It can also be installed through graphical software managers (KDE Discover, GNOM
 
 ### AppImage
 
+AppImages are published for both **x86_64** and **aarch64** (ARM64). Pick the file matching your CPU — the ARM64 build has `aarch64` in its name (e.g. `OrcaSlicer_Linux_AppImage_Ubuntu2404_aarch64_*.AppImage`).
+
  1. Download App image from the [releases page](https://github.com/OrcaSlicer/OrcaSlicer/releases).
  2. Double click the downloaded file to run it.
 

resources/shaders/110/phong.fs

@@ -10,18 +10,18 @@ const float EPSILON = 0.0001;
 
 // normalized values for (-0.6/1.31, 0.6/1.31, 1./1.31)
 const vec3 LIGHT_TOP_DIR = vec3(-0.4574957, 0.4574957, 0.7624929);
-#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_DIFFUSE    (0.85 * INTENSITY_CORRECTION)
-#define LIGHT_TOP_SPECULAR   (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.35 * INTENSITY_CORRECTION)
-#define LIGHT_TOP_SHININESS  128.0
+#define LIGHT_TOP_SHININESS  32.0
 
 // normalized values for (1./1.43, 0.2/1.43, 1./1.43)
 const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
-#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+#define LIGHT_FRONT_DIFFUSE  (0.35 * INTENSITY_CORRECTION)
-#define LIGHT_FRONT_SPECULAR (0.28 * INTENSITY_CORRECTION)
+#define LIGHT_FRONT_SPECULAR (0.12 * INTENSITY_CORRECTION)
-#define LIGHT_FRONT_SHININESS 64.0
+#define LIGHT_FRONT_SHININESS 16.0
 
-#define INTENSITY_AMBIENT    0.22
+#define INTENSITY_AMBIENT    0.25
-#define WINDOW_REFLECTION_INTENSITY 0.55
+#define WINDOW_REFLECTION_INTENSITY 0.30
 
 struct PrintVolumeDetection
 {
@@ -162,11 +162,11 @@ vec3 compute_window_reflection(vec3 normal, vec3 view_dir)
     float bars = 1.0;
     
     // Fresnel effect for edge glow
-    float fresnel = pow(1.0 - max(dot(normal, view_dir), 0.0), 1.0);
+    float fresnel = pow(1.0 - max(dot(normal, view_dir), 0.0), 1.2);
     float facing = smoothstep(-0.4, 0.6, reflect_light.z);
     
-    float intensity = window_light * bars * (0.25 + 0.25 * fresnel) * facing;
+    float intensity = window_light * bars * (0.15 + 0.15 * fresnel) * facing;
-    intensity = clamp(intensity, 0.0, 0.45);
+    intensity = clamp(intensity, 0.0, 0.25);
     
     return vec3(intensity);
 }

resources/shaders/140/phong.fs

@@ -10,18 +10,18 @@ const float EPSILON = 0.0001;
 
 // normalized values for (-0.6/1.31, 0.6/1.31, 1./1.31)
 const vec3 LIGHT_TOP_DIR = vec3(-0.4574957, 0.4574957, 0.7624929);
-#define LIGHT_TOP_DIFFUSE    (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_DIFFUSE    (0.85 * INTENSITY_CORRECTION)   
-#define LIGHT_TOP_SPECULAR   (0.8 * INTENSITY_CORRECTION)
+#define LIGHT_TOP_SPECULAR   (0.35 * INTENSITY_CORRECTION)   
-#define LIGHT_TOP_SHININESS  128.0
+#define LIGHT_TOP_SHININESS  32.0                           
 
 // normalized values for (1./1.43, 0.2/1.43, 1./1.43)
 const vec3 LIGHT_FRONT_DIR = vec3(0.6985074, 0.1397015, 0.6985074);
-#define LIGHT_FRONT_DIFFUSE  (0.3 * INTENSITY_CORRECTION)
+#define LIGHT_FRONT_DIFFUSE  (0.35 * INTENSITY_CORRECTION)   
-#define LIGHT_FRONT_SPECULAR (0.28 * INTENSITY_CORRECTION)
+#define LIGHT_FRONT_SPECULAR (0.12 * INTENSITY_CORRECTION)   
-#define LIGHT_FRONT_SHININESS 64.0
+#define LIGHT_FRONT_SHININESS 16.0                           
 
-#define INTENSITY_AMBIENT    0.22
+#define INTENSITY_AMBIENT    0.25                            
-#define WINDOW_REFLECTION_INTENSITY 0.55
+#define WINDOW_REFLECTION_INTENSITY 0.30                    
 
 struct PrintVolumeDetection
 {
@@ -164,12 +164,13 @@ vec3 compute_window_reflection(vec3 normal, vec3 view_dir)
     // No bars - just pure circular glass
     float bars = 1.0;
     
-    // Fresnel effect for edge glow
+
-    float fresnel = pow(1.0 - max(dot(normal, view_dir), 0.0), 1.0);
+    float fresnel = pow(1.0 - max(dot(normal, view_dir), 0.0), 1.2);
     float facing = smoothstep(-0.4, 0.6, reflect_light.z);
     
-    float intensity = window_light * bars * (0.25 + 0.25 * fresnel) * facing;
+
-    intensity = clamp(intensity, 0.0, 0.45);
+    float intensity = window_light * bars * (0.15 + 0.15 * fresnel) * facing;
+    intensity = clamp(intensity, 0.0, 0.25);  
     
     return vec3(intensity);
 }

scripts/flatpak/com.orcaslicer.OrcaSlicer.metainfo.xml

@@ -45,8 +45,8 @@
         <color type="primary" scheme_preference="dark">#00695C</color>
     </branding>
     <releases>
-        <release version="2.4.0-dev" date="2026-05-22" type="development">
+        <release version="2.4.0" date="2026-06-08" type="development">
-            <url type="details">https://github.com/OrcaSlicer/OrcaSlicer/releases/tag/nightly-builds</url>
+            <url type="details">https://github.com/OrcaSlicer/OrcaSlicer/releases/tag/2.4.0</url>
             <description>
                 <p>See the release page for detailed changelog.</p>
             </description>

src/libslic3r/AppConfig.cpp

@@ -276,6 +276,9 @@ void AppConfig::set_defaults()
     if (get(SETTING_OPENGL_PHONG_BASIC_PLATE_SHADOWS).empty())
         set_bool(SETTING_OPENGL_PHONG_BASIC_PLATE_SHADOWS, false);
 
+    if (get(SETTING_OPENGL_PHONG_SMOOTH_NORMALS).empty())
+        set_bool(SETTING_OPENGL_PHONG_SMOOTH_NORMALS, false);
+
     if (get(SETTING_OPENGL_PHONG_SSAO).empty())
         set_bool(SETTING_OPENGL_PHONG_SSAO, false);
 

src/libslic3r/AppConfig.hpp

@@ -39,6 +39,7 @@ using namespace nlohmann;
 #define SETTING_OPENGL_SHADING_MODEL "opengl_shading_model"
 #define SETTING_OPENGL_PHONG_BASIC_PLATE_SHADOWS "opengl_phong_basic_plate_shadows"
 #define SETTING_OPENGL_PHONG_SSAO "opengl_phong_ssao"
+#define SETTING_OPENGL_PHONG_SMOOTH_NORMALS "opengl_phong_smooth_normals"
 
 #if defined(_WIN32) || defined(_WIN64)
 #define BAMBU_NETWORK_AGENT_VERSION_LEGACY "01.10.01.09"

src/libslic3r/Brim.cpp

@@ -879,7 +879,9 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
     std::map<ObjectID, ExtrusionEntityCollection>& brimMap,
     std::map<ObjectID, ExtrusionEntityCollection>& supportBrimMap,
     std::vector<std::pair<ObjectID, unsigned int>> &objPrintVec,
-    std::vector<unsigned int>& printExtruders)
+    std::vector<unsigned int>& printExtruders,
+    std::map<ObjectID, ExPolygons>* objectBrimAreasOut,
+    std::map<ObjectID, ExPolygons>* supportBrimAreasOut)
 {
     std::map<ObjectID, double> brim_width_map;
     std::map<ObjectID, ExPolygons> brimAreaMap;
@@ -928,12 +930,25 @@ void make_brim(const Print& print, PrintTryCancel try_cancel, Polygons& islands_
     for (size_t iia = 0; iia < islands_area.size(); ++iia)
         islands_area[iia].translate(plate_shift);
 
+    // Orca: keep translated brim footprints for skirt grouping.
+    auto translate_area_map = [plate_shift](const std::map<ObjectID, ExPolygons>& src) {
+        std::map<ObjectID, ExPolygons> dst = src;
+        for (auto& [_, areas] : dst)
+            for (ExPolygon& area : areas)
+                area.translate(plate_shift);
+        return dst;
+    };
+    if (objectBrimAreasOut != nullptr)
+        *objectBrimAreasOut = translate_area_map(brimAreaMap);
+    if (supportBrimAreasOut != nullptr)
+        *supportBrimAreasOut = translate_area_map(supportBrimAreaMap);
+
     const bool combine_brims     = print.config().combine_brims.value;
     const bool is_by_object      = (print.config().print_sequence == PrintSequence::ByObject);
     const bool can_combine_brims = combine_brims && !is_by_object;
 
     if (!can_combine_brims) {
-        // Orca: Generate brims separately for each object when multiple extruders are used
+        // Orca: Generate brims separately when brims cannot be combined.
         for (auto iter = brimAreaMap.begin(); iter != brimAreaMap.end(); ++iter) {
             if (!iter->second.empty()) {
                 brimMap.insert(std::make_pair(iter->first, makeBrimInfill(iter->second, print, islands_area)));

src/libslic3r/Brim.hpp

@@ -1,6 +1,7 @@
 #ifndef slic3r_Brim_hpp_
 #define slic3r_Brim_hpp_
 
+#include "ExPolygon.hpp"
 #include "Point.hpp"
 
 #include<map>
@@ -19,7 +20,9 @@ void make_brim(const Print& print, PrintTryCancel try_cancel,
     Polygons& islands_area, std::map<ObjectID, ExtrusionEntityCollection>& brimMap,
     std::map<ObjectID, ExtrusionEntityCollection>& supportBrimMap,
     std::vector<std::pair<ObjectID, unsigned int>>& objPrintVec,
-    std::vector<unsigned int>& printExtruders);
+    std::vector<unsigned int>& printExtruders,
+    std::map<ObjectID, ExPolygons>* objectBrimAreasOut = nullptr,
+    std::map<ObjectID, ExPolygons>* supportBrimAreasOut = nullptr);
 
 // BBS: automatically make brim
 ExtrusionEntityCollection make_brim_auto(const Print &print, PrintTryCancel try_cancel, Polygons &islands_area);

src/libslic3r/GCode.cpp

@@ -5151,44 +5151,30 @@ LayerResult GCode::process_layer(
     bool has_insert_wrapping_detection_gcode = false;
 
     // Extrude the skirt, brim, support, perimeters, infill ordered by the extruders.
-    // Orca: Print unified global brim before any object.
-    // Only do this if `combine_brims` is enabled and we are printing by layer.
-    if (first_layer && sequence_by_layer && m_config.combine_brims && !print.m_brimMap.empty()) {
-        const ObjectID unified_object_id = [&]() -> ObjectID {
-            ObjectID id;
-            bool     found = false;
-            for (const auto& [obj_id, brim] : print.m_brimMap) {
-                const bool has_printable_entities = std::any_of(brim.entities.begin(), brim.entities.end(),
-                                                                [](const ExtrusionEntity* ee) { return ee != nullptr; });
-                if (!has_printable_entities)
-                    continue;
-                if (found)
-                    return ObjectID();
-                id    = obj_id;
-                found = true;
-            }
-            return found ? id : ObjectID();
-        }();
-
-        if (unified_object_id.valid()) {
-            const auto it = print.m_brimMap.find(unified_object_id);
-            if (it != print.m_brimMap.end()) {
-                this->set_origin(0., 0.);
-                for (const ExtrusionEntity* ee : it->second.entities)
-                    if (ee != nullptr)
-                        gcode += this->extrude_entity(*ee, "brim", m_config.support_speed.value);
-
-                // Mark brim as printed for this object to avoid per-object brim emission later.
-                this->m_objsWithBrim.erase(unified_object_id);
-            }
-        }
-    }
-
     for (unsigned int extruder_id : layer_tools.extruders)
     {
-        if (print.config().skirt_type == stCombined && !print.skirt().empty())
+        if ((print.config().skirt_type == stCombined ||
-            gcode += generate_skirt(print, print.skirt(), Point(0, 0), layer.object()->config().skirt_start_angle, layer_tools, layer,
+             (print.config().skirt_type == stPerObject && print.config().print_sequence == PrintSequence::ByLayer)) &&
-                                    extruder_id);
+            !print.skirt_groups().empty()) {
+            bool skirt_generated_for_current_print_z = false;
+            for (const ExtrusionEntityCollection& skirt_group : print.skirt_groups()) {
+                if (skirt_group.empty())
+                    continue;
+
+                // Orca: each grouped skirt is emitted as its own collection so higher skirt layers
+                // follow the same per-group behavior as the first layer.
+                if (first_layer)
+                    m_skirt_done.clear();
+                else if (skirt_generated_for_current_print_z && !m_skirt_done.empty())
+                    m_skirt_done.pop_back();
+
+                std::string skirt_gcode = generate_skirt(print, skirt_group, Point(0, 0), layer.object()->config().skirt_start_angle,
+                                                          layer_tools, layer, extruder_id);
+                if (!skirt_gcode.empty())
+                    skirt_generated_for_current_print_z = true;
+                gcode += std::move(skirt_gcode);
+            }
+        }
 
         if (print.config().print_sequence == PrintSequence::ByLayer && m_enable_exclude_object && print.config().support_object_skip_flush.value) {
             std::vector<size_t> filament_instances_id;
@@ -5289,6 +5275,37 @@ LayerResult GCode::process_layer(
             }
         }
 
+        // Orca: Print unified global brim after the skirt and before any object.
+        // Only do this if `combine_brims` is enabled and we are printing by layer.
+        if (first_layer && sequence_by_layer && m_config.combine_brims && !print.m_brimMap.empty()) {
+            const ObjectID unified_object_id = [&]() -> ObjectID {
+                ObjectID id;
+                for (const auto& [obj_id, brim] : print.m_brimMap) {
+                    const bool has_printable_entities = std::any_of(brim.entities.begin(), brim.entities.end(),
+                                                                    [](const ExtrusionEntity* ee) { return ee != nullptr; });
+                    if (!has_printable_entities)
+                        continue;
+
+                    if (id.valid())
+                        return ObjectID();
+
+                    id = obj_id;
+                }
+                return id;
+            }();
+
+            if (unified_object_id.valid() && this->m_objsWithBrim.find(unified_object_id) != this->m_objsWithBrim.end()) {
+                const ExtrusionEntityCollection& unified_brim = print.m_brimMap.at(unified_object_id);
+                this->set_origin(0., 0.);
+                for (const ExtrusionEntity* ee : unified_brim.entities)
+                    if (ee != nullptr)
+                        gcode += this->extrude_entity(*ee, "brim", m_config.support_speed.value);
+
+                // Mark brim as printed for this object to avoid per-object brim emission later.
+                this->m_objsWithBrim.erase(unified_object_id);
+            }
+        }
+
         // We are almost ready to print. However, we must go through all the objects twice to print the the overridden extrusions first (infill/perimeter wiping feature):
         std::vector<ObjectByExtruder::Island::Region> by_region_per_copy_cache;
         for (int print_wipe_extrusions = is_anything_overridden; print_wipe_extrusions>=0; --print_wipe_extrusions) {

src/libslic3r/Print.cpp

@@ -23,6 +23,7 @@
 
 #include <algorithm>
 #include <limits>
+#include <numeric>
 #include <unordered_set>
 #include <boost/filesystem/path.hpp>
 #include <boost/format.hpp>
@@ -2442,7 +2443,10 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
             start_time = (long long)Slic3r::Utils::get_current_time_utc();
 
         m_skirt.clear();
+        m_skirt_groups.clear();
         m_skirt_convex_hull.clear();
+        m_objectBrimAreas.clear();
+        m_supportBrimAreas.clear();
         m_first_layer_convex_hull.points.clear();
         for (PrintObject *object : m_objects)  object->m_skirt.clear();
 
@@ -2536,7 +2540,7 @@ void Print::process(long long *time_cost_with_cache, bool use_cache)
         if (this->has_brim()) {
             Polygons islands_area;
             make_brim(*this, this->make_try_cancel(), islands_area, m_brimMap,
-                m_supportBrimMap, objPrintVec, printExtruders);
+                m_supportBrimMap, objPrintVec, printExtruders, &m_objectBrimAreas, &m_supportBrimAreas);
             for (Polygon& poly_ex : islands_area)
                 poly_ex.douglas_peucker(SCALED_RESOLUTION);
             for (Polygon &poly : union_(this->first_layer_islands(), islands_area))
@@ -2658,11 +2662,13 @@ void Print::_make_skirt()
         skirt_height_z = std::max(skirt_height_z, object->m_layers[skirt_layers-1]->print_z);
     }
 
-    // Collect points from all layers contained in skirt height.
+    struct ObjectSkirtHull {
-    Points points;
+        PrintObject* object;
+        Polygon      hull;
+    };
 
-    // BBS
+    // Orca: build one local occupied hull per object from object and support geometry up to skirt height.
-    std::map<PrintObject*, Polygon> object_convex_hulls;
+    std::vector<ObjectSkirtHull> object_convex_hulls;
     for (PrintObject *object : m_objects) {
         Points object_points;
         // Get object layers up to skirt_height_z.
@@ -2680,30 +2686,13 @@ void Print::_make_skirt()
             layer->support_fills.collect_points(object_points);
         }
 
-        object_convex_hulls.insert({ object, Slic3r::Geometry::convex_hull(object_points) });
+        object_convex_hulls.push_back({ object, Slic3r::Geometry::convex_hull(object_points) });
-
-        // Repeat points for each object copy.
-        for (const PrintInstance &instance : object->instances()) {
-            Points copy_points = object_points;
-            for (Point &pt : copy_points)
-                pt += instance.shift;
-            append(points, copy_points);
-        }
     }
 
-    // Include the wipe tower.
+    if (object_convex_hulls.empty())
-    append(points, this->first_layer_wipe_tower_corners());
-
-    // Unless draft shield is enabled, include all brims as well.
-    if (config().draft_shield == dsDisabled)
-        append(points, m_first_layer_convex_hull.points);
-
-    if (points.size() < 3)
-        // At least three points required for a convex hull.
         return;
 
     this->throw_if_canceled();
-    Polygon convex_hull = Slic3r::Geometry::convex_hull(points);
 
     // Skirt may be printed on several layers, having distinct layer heights,
     // but loops must be aligned so can't vary width/spacing
@@ -2725,13 +2714,13 @@ void Print::_make_skirt()
         }
     }
 
-    // Initial offset of the brim inner edge from the object (possible with a support & raft).
+    // Initial skirt centerline offset from the occupied outline.
-    // The skirt will touch the brim if the brim is extruded.
+    // The skirt will touch the occupied outline if skirt_distance is zero.
-    auto   distance = float(scale_(m_config.skirt_distance.value - spacing/2.));
+    // Generate loops inward to outward; callers reverse them before G-code export.
-    // Draw outlines from outside to inside.
     // Loop while we have less skirts than required or any extruder hasn't reached the min length if any.
-    std::vector<coordf_t> extruded_length(extruders.size(), 0.);
+    auto append_skirt_loops_for_hull = [&](const Polygon& hull, ExtrusionEntityCollection& dst, bool collect_skirt_hull) {
-    if (m_config.skirt_type == stCombined) {
+        float distance = float(scale_(m_config.skirt_distance.value - spacing/2.));
+        std::vector<coordf_t> extruded_length(extruders.size(), 0.);
         for (size_t i = m_config.skirt_loops, extruder_idx = 0; i > 0; -- i) {
             this->throw_if_canceled();
             // Offset the skirt outside.
@@ -2739,8 +2728,8 @@ void Print::_make_skirt()
             // Generate the skirt centerline.
             Polygon loop;
             {
-                // BBS. skirt_distance is defined as the gap between skirt and outer most brim, so no need to add max_brim_width
+                // Orca: the hull already represents the occupied outline used for this skirt.
-                Polygons loops = offset(convex_hull, distance, ClipperLib::jtRound, float(scale_(0.1)));
+                Polygons loops = offset(hull, distance, ClipperLib::jtRound, float(scale_(0.1)));
                 Geometry::simplify_polygons(loops, scale_(0.05), &loops);
 			    if (loops.empty())
 				    break;
@@ -2756,7 +2745,7 @@ void Print::_make_skirt()
 				    (float)initial_layer_print_height  // this will be overridden at G-code export time
                 )));
             eloop.paths.back().polyline = Polyline3(loop.split_at_first_point());
-            m_skirt.append(eloop);
+            dst.append(eloop);
             if (m_config.min_skirt_length.value > 0) {
                 // The skirt length is limited. Sum the total amount of filament length extruded, in mm.
                 extruded_length[extruder_idx] += unscale<double>(loop.length()) * extruders_e_per_mm[extruder_idx];
@@ -2772,69 +2761,147 @@ void Print::_make_skirt()
                         ++ extruder_idx;
                 }
             } else {
-                // The skirt lenght is not limited, extrude the skirt with the 1st extruder only.
+                // The skirt length is not limited, extrude the skirt with the 1st extruder only.
             }
         }
-    } else {
-        m_skirt.clear();
-    }
-    // Brims were generated inside out, reverse to print the outmost contour first.
-    m_skirt.reverse();
 
-    // Remember the outer edge of the last skirt line extruded as m_skirt_convex_hull.
+        if (collect_skirt_hull)
-    for (Polygon &poly : offset(convex_hull, distance + 0.5f * float(scale_(spacing)), ClipperLib::jtRound, float(scale_(0.1))))
+            for (Polygon &poly : offset(hull, distance + 0.5f * float(scale_(spacing)), ClipperLib::jtRound, float(scale_(0.1))))
-        append(m_skirt_convex_hull, std::move(poly.points));
+                append(m_skirt_convex_hull, std::move(poly.points));
+    };
 
-    if (m_config.skirt_type == stPerObject) {
+    m_skirt.clear();
-        // BBS
+    m_skirt_groups.clear();
-        for (auto obj_cvx_hull : object_convex_hulls) {
-            double object_skirt_distance = float(scale_(m_config.skirt_distance.value - spacing/2.));
-            PrintObject* object = obj_cvx_hull.first;
-            object->m_skirt.clear();
-            extruded_length.assign(extruded_length.size(), 0.);
-            for (size_t i = m_config.skirt_loops.value, extruder_idx = 0; i > 0; -- i) {
-                object_skirt_distance += float(scale_(spacing));
-                Polygon loop;
-                {
-                    // BBS. skirt_distance is defined as the gap between skirt and outer most brim, so no need to add max_brim_width
-                    Polygons loops = offset(obj_cvx_hull.second, object_skirt_distance, ClipperLib::jtRound, float(scale_(0.1)));
-                    Geometry::simplify_polygons(loops, scale_(0.05), &loops);
-                    if (loops.empty())
-                        break;
-                    loop = loops.front();
-                }
 
-                // Extrude the skirt loop.
+    if (m_config.skirt_type == stPerObject && m_config.print_sequence == PrintSequence::ByObject) {
-                ExtrusionLoop eloop(elrSkirt);
+        for (const ObjectSkirtHull& object_hull : object_convex_hulls) {
-                eloop.paths.emplace_back(ExtrusionPath(
+            object_hull.object->m_skirt.clear();
-                    ExtrusionPath(
+            append_skirt_loops_for_hull(object_hull.hull, object_hull.object->m_skirt, false);
-                        erSkirt,
+            object_hull.object->m_skirt.reverse();
-                        (float)mm3_per_mm,         // this will be overridden at G-code export time
+        }
-                        flow.width(),
+    } else if (m_config.skirt_type == stCombined || m_config.skirt_type == stPerObject) {
-                        (float)initial_layer_print_height  // this will be overridden at G-code export time
+        struct SkirtGroupItem {
-                    )));
+            Points       occupied_points;
-                eloop.paths.back().polyline = Polyline3(loop.split_at_first_point());
+            bool         emits_skirt;
-                object->m_skirt.append(std::move(eloop));
+        };
-                if (m_config.min_skirt_length.value > 0) {
-                    // The skirt length is limited. Sum the total amount of filament length extruded, in mm.
-                    extruded_length[extruder_idx] += unscale<double>(loop.length()) * extruders_e_per_mm[extruder_idx];
-                    if (extruded_length[extruder_idx] < m_config.min_skirt_length.value) {
-                        // Not extruded enough yet with the current extruder. Add another loop.
-                        if (i == 1)
-                            ++ i;
-                    } else {
-                        assert(extruded_length[extruder_idx] >= m_config.min_skirt_length.value);
-                        // Enough extruded with the current extruder. Extrude with the next one,
-                        // until the prescribed number of skirt loops is extruded.
-                        if (extruder_idx + 1 < extruders.size())
-                            ++ extruder_idx;
-                    }
-                } else {
-                    // The skirt lenght is not limited, extrude the skirt with the 1st extruder only.
-                }
 
+        // Orca: group items represent occupied first-layer areas. Object items emit skirts;
+        // obstacle-only items, such as wipe tower, only force nearby object groups to merge.
+        std::vector<SkirtGroupItem> group_items;
+        const coord_t grouping_offset = scale_(m_config.skirt_distance.value + m_config.skirt_loops.value * spacing);
+        for (const ObjectSkirtHull& object_hull : object_convex_hulls) {
+            PrintObject* object = object_hull.object;
+            Points occupied_points;
+            for (const PrintInstance &instance : object->instances()) {
+                Points copy_points = object_hull.hull.points;
+                for (Point &pt : copy_points)
+                    pt += instance.shift;
+                append(occupied_points, copy_points);
+            }
+
+            auto append_brim_points = [&occupied_points](const ExPolygons& areas) {
+                for (const ExPolygon& area : areas)
+                    append(occupied_points, area.contour.points);
+            };
+            if (auto it = m_objectBrimAreas.find(object->id()); it != m_objectBrimAreas.end())
+                append_brim_points(it->second);
+            if (auto it = m_supportBrimAreas.find(object->id()); it != m_supportBrimAreas.end())
+                append_brim_points(it->second);
+            if (occupied_points.size() < 3)
+                continue;
+
+            // Orca: include the object's brim/support-brim footprint before checking skirt collisions.
+            group_items.push_back({ std::move(occupied_points), true });
+        }
+
+        // Orca: the wipe tower contributes occupied area, but does not emit a skirt by itself.
+        Points wipe_tower_points = this->first_layer_wipe_tower_corners();
+        if (wipe_tower_points.size() >= 3)
+            group_items.push_back({ std::move(wipe_tower_points), false });
+
+        std::vector<size_t> parent(group_items.size());
+        std::iota(parent.begin(), parent.end(), 0);
+        // Orca: union-find keeps collision merging local without repeatedly rebuilding item lists.
+        auto find_parent = [&parent](size_t idx) {
+            while (parent[idx] != idx) {
+                parent[idx] = parent[parent[idx]];
+                idx = parent[idx];
+            }
+            return idx;
+        };
+        auto unite = [&parent, &find_parent](size_t a, size_t b) {
+            a = find_parent(a);
+            b = find_parent(b);
+            if (a != b)
+                parent[b] = a;
+        };
+
+        // Orca: combined skirt is the same grouping model with all items forced into one group.
+        if (m_config.skirt_type == stCombined && !group_items.empty())
+            for (size_t i = 1; i < group_items.size(); ++i)
+                unite(0, i);
+
+        auto build_grouped_points = [&]() {
+            struct GroupData {
+                Points points;
+                bool   emits_skirt = false;
+            };
+
+            std::map<size_t, GroupData> grouped;
+            for (size_t i = 0; i < group_items.size(); ++i) {
+                GroupData& group = grouped[find_parent(i)];
+                append(group.points, group_items[i].occupied_points);
+                group.emits_skirt = group.emits_skirt || group_items[i].emits_skirt;
+            }
+            return grouped;
+        };
+
+        bool groups_changed = m_config.skirt_type == stPerObject;
+        while (groups_changed) {
+            groups_changed = false;
+            auto grouped_points = build_grouped_points();
+            std::vector<std::pair<size_t, Polygon>> group_envelopes;
+            for (const auto& [root, group] : grouped_points) {
+                if (group.points.size() < 3)
+                    continue;
+
+                // Orca: emitting groups are expanded to their final skirt reach; obstacle groups are not.
+                Polygon envelope = Geometry::convex_hull(group.points);
+                if (group.emits_skirt) {
+                    // Orca: merge groups when a skirt envelope intersects another group or obstacle.
+                    Polygons envelopes = offset(envelope, grouping_offset, ClipperLib::jtRound, float(scale_(0.1)));
+                    if (envelopes.empty())
+                        continue;
+                    envelope = std::move(envelopes.front());
+                }
+                group_envelopes.emplace_back(root, std::move(envelope));
+            }
+
+            for (size_t i = 0; i < group_envelopes.size(); ++i) {
+                for (size_t j = i + 1; j < group_envelopes.size(); ++j) {
+                    const size_t root_i = find_parent(group_envelopes[i].first);
+                    const size_t root_j = find_parent(group_envelopes[j].first);
+                    if (root_i != root_j && !intersection(group_envelopes[i].second, group_envelopes[j].second).empty()) {
+                        unite(root_i, root_j);
+                        groups_changed = true;
+                    }
+                }
+            }
+        }
+
+        auto grouped_points = build_grouped_points();
+        for (auto& [_, group] : grouped_points) {
+            if (!group.emits_skirt || group.points.size() < 3)
+                continue;
+            // Orca: after merging, use the occupied outline directly; do not add skirt distance twice.
+            ExtrusionEntityCollection group_skirt;
+            append_skirt_loops_for_hull(Geometry::convex_hull(group.points), group_skirt, true);
+            if (!group_skirt.empty()) {
+                group_skirt.reverse();
+                // Orca: keep m_skirt as a flattened compatibility mirror for preview/extents.
+                m_skirt.append(group_skirt.entities);
+                m_skirt_groups.push_back(std::move(group_skirt));
             }
-            object->m_skirt.reverse();
         }
     }
 }

src/libslic3r/Print.hpp

@@ -971,6 +971,7 @@ public:
     PrintRegionPtrs&            print_regions_mutable() { return m_print_regions; }
     std::vector<size_t>         layers_sorted_for_object(float start, float end, std::vector<LayerPtrs> &layers_of_objects, std::vector<BoundingBox> &boundingBox_for_objects, VecOfPoints& objects_instances_shift);
     const ExtrusionEntityCollection& skirt() const { return m_skirt; }
+    const std::vector<ExtrusionEntityCollection>& skirt_groups() const { return m_skirt_groups; }
     // Convex hull of the 1st layer extrusions, for bed leveling and placing the initial purge line.
     // It encompasses the object extrusions, support extrusions, skirt, brim, wipe tower.
     // It does NOT encompass user extrusions generated by custom G-code,
@@ -1144,9 +1145,13 @@ private:
 
     // Ordered collections of extrusion paths to build skirt loops and brim.
     ExtrusionEntityCollection               m_skirt;
+    std::vector<ExtrusionEntityCollection>  m_skirt_groups;
     // BBS: collecting extrusion paths to build brim by objs
     std::map<ObjectID, ExtrusionEntityCollection>         m_brimMap;
     std::map<ObjectID, ExtrusionEntityCollection>         m_supportBrimMap;
+    // Orca: cached occupied brim footprints used when grouping per-object skirts.
+    std::map<ObjectID, ExPolygons>                        m_objectBrimAreas;
+    std::map<ObjectID, ExPolygons>                        m_supportBrimAreas;
     // Convex hull of the 1st layer extrusions.
     // It encompasses the object extrusions, support extrusions, skirt, brim, wipe tower.
     // It does NOT encompass user extrusions generated by custom G-code,

src/libslic3r/Technologies.hpp

@@ -24,8 +24,7 @@
 
 // Enable rendering of objects using environment map
 #define ENABLE_ENVIRONMENT_MAP 0
-// Enable smoothing of objects normals
+
-#define ENABLE_SMOOTH_NORMALS 0
 // Enable rendering markers for options in preview as fixed screen size points
 #define ENABLE_FIXED_SCREEN_SIZE_POINT_MARKERS 1
 

src/slic3r/GUI/3DScene.cpp

@@ -759,12 +759,8 @@ int GLVolumeCollection::load_object_volume(
     v.set_color(color_from_model_volume(*model_volume));
     v.name = model_volume->name;
 
-#if ENABLE_SMOOTH_NORMALS
-    v.model.init_from(mesh, true);
-#else
     v.model.init_from(*mesh);
     if (need_raycaster) { v.mesh_raycaster = std::make_unique<GUI::MeshRaycaster>(mesh); }
-#endif // ENABLE_SMOOTH_NORMALS
     v.composite_id = GLVolume::CompositeID(obj_idx, volume_idx, instance_idx);
 
     if (model_volume->is_model_part())
@@ -815,13 +811,9 @@ void GLVolumeCollection::load_object_auxiliary(
         const ModelInstance& model_instance = *print_object->model_object()->instances[instance_idx.first];
         this->volumes.emplace_back(new GLVolume((milestone == slaposPad) ? GLVolume::SLA_PAD_COLOR : GLVolume::SLA_SUPPORT_COLOR));
         GLVolume& v = *this->volumes.back();
-#if ENABLE_SMOOTH_NORMALS
-        v.model.init_from(mesh, true);
-#else
         v.model.init_from(mesh);
         v.model.set_color((milestone == slaposPad) ? GLVolume::SLA_PAD_COLOR : GLVolume::SLA_SUPPORT_COLOR);
         v.mesh_raycaster = std::make_unique<GUI::MeshRaycaster>(std::make_shared<const TriangleMesh>(mesh));
-#endif // ENABLE_SMOOTH_NORMALS
         v.composite_id = GLVolume::CompositeID(obj_idx, -int(milestone), (int)instance_idx.first);
         v.geometry_id = std::pair<size_t, size_t>(timestamp, model_instance.id().id);
         // Create a copy of the convex hull mesh for each instance. Use a move operator on the last instance.

src/slic3r/GUI/GLCanvas3D.cpp

@@ -2793,22 +2793,14 @@ void GLCanvas3D::reload_scene(bool refresh_immediately, bool force_full_scene_re
                                 TriangleMesh mesh = print_object->get_mesh(slaposDrillHoles);
 	                            assert(! mesh.empty());
                                 mesh.transform(sla_print->sla_trafo(*m_model->objects[volume.object_idx()]).inverse());
-#if ENABLE_SMOOTH_NORMALS
-                                volume.model.init_from(mesh, true);
-#else
                                 volume.model.init_from(mesh);
                                 volume.mesh_raycaster = std::make_unique<GUI::MeshRaycaster>(std::make_shared<TriangleMesh>(mesh));
-#endif // ENABLE_SMOOTH_NORMALS
                             }
                             else {
 	                        	// Reload the original volume.
-#if ENABLE_SMOOTH_NORMALS
-                                volume.model.init_from(m_model->objects[volume.object_idx()]->volumes[volume.volume_idx()]->mesh(), true);
-#else
                                 const TriangleMesh& new_mesh = m_model->objects[volume.object_idx()]->volumes[volume.volume_idx()]->mesh();
                                 volume.model.init_from(new_mesh);
                                 volume.mesh_raycaster = std::make_unique<GUI::MeshRaycaster>(std::make_shared<TriangleMesh>(new_mesh));
-#endif // ENABLE_SMOOTH_NORMALS
                             }
 	                    }
                     	//FIXME it is an ugly hack to write the timestamp into the "offsets" field to not have to add another member variable
@@ -10001,11 +9993,7 @@ void GLCanvas3D::_load_sla_shells()
         const TriangleMesh& mesh, const ColorRGBA& color, bool outside_printer_detection_enabled) {
         m_volumes.volumes.emplace_back(new GLVolume(color));
         GLVolume& v = *m_volumes.volumes.back();
-#if ENABLE_SMOOTH_NORMALS
-        v.model.init_from(mesh, true);
-#else
         v.model.init_from(mesh);
-#endif // ENABLE_SMOOTH_NORMALS
         v.shader_outside_printer_detection_enabled = outside_printer_detection_enabled;
         v.composite_id.volume_id = volume_id;
         v.set_instance_offset(unscale(instance.shift.x(), instance.shift.y(), 0.0));

src/slic3r/GUI/GLModel.cpp

@@ -14,18 +14,20 @@
 #include <boost/filesystem/operations.hpp>
 #include <boost/algorithm/string/predicate.hpp>
 
-#if ENABLE_SMOOTH_NORMALS
+#if defined(L)
+#undef L
+#endif
+
 #include <igl/per_face_normals.h>
 #include <igl/per_corner_normals.h>
 #include <igl/per_vertex_normals.h>
-#endif // ENABLE_SMOOTH_NORMALS
+
 
 #include <glad/gl.h>
 
 namespace Slic3r {
 namespace GUI {
 
-#if ENABLE_SMOOTH_NORMALS
 static void smooth_normals_corner(const TriangleMesh& mesh, std::vector<stl_normal>& normals)
 {
     using MapMatrixXfUnaligned = Eigen::Map<const Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor | Eigen::DontAlign>>;
@@ -41,7 +43,7 @@ static void smooth_normals_corner(const TriangleMesh& mesh, std::vector<stl_norm
         Eigen::Index(face_normals.size()), 3).cast<double>();
     Eigen::MatrixXd out_normals;
 
-    igl::per_corner_normals(vertices, indices, in_normals, 1.0, out_normals);
+    igl::per_corner_normals(vertices, indices, 1.0, out_normals);
 
     normals = std::vector<stl_normal>(mesh.its.vertices.size());
     for (size_t i = 0; i < mesh.its.indices.size(); ++i) {
@@ -50,7 +52,6 @@ static void smooth_normals_corner(const TriangleMesh& mesh, std::vector<stl_norm
         }
     }
 }
-#endif // ENABLE_SMOOTH_NORMALS
 
 void GLModel::Geometry::add_vertex(const Vec2f& position)
 {
@@ -455,17 +456,41 @@ void GLModel::init_from(const indexed_triangle_set& its)
     data.reserve_vertices(3 * its.indices.size());
     data.reserve_indices(3 * its.indices.size());
 
-    // vertices + indices
+    // Read user preference: smooth normals enabled
-    unsigned int vertices_counter = 0;
+    const bool realistic_mode = wxGetApp().app_config != nullptr && wxGetApp().app_config->get_bool(SETTING_OPENGL_REALISTIC_MODE);
-    for (uint32_t i = 0; i < its.indices.size(); ++i) {
+    const bool smooth_normals_enabled = wxGetApp().app_config != nullptr && wxGetApp().app_config->get_bool(SETTING_OPENGL_PHONG_SMOOTH_NORMALS);
-        const stl_triangle_vertex_indices face = its.indices[i];
+
-        const stl_vertex                  vertex[3] = { its.vertices[face[0]], its.vertices[face[1]], its.vertices[face[2]] };
+    if (realistic_mode && smooth_normals_enabled) {
-        const stl_vertex                  n = face_normal_normalized(vertex);
+        // Use per-corner smooth normals (via IGL)
-        for (size_t j = 0; j < 3; ++j) {
+        using MapMatrixXfUnaligned = Eigen::Map<const Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor | Eigen::DontAlign>>;
-            data.add_vertex(vertex[j], n);
+        using MapMatrixXiUnaligned = Eigen::Map<const Eigen::Matrix<int, Eigen::Dynamic, Eigen::Dynamic, Eigen::RowMajor | Eigen::DontAlign>>;
+        Eigen::MatrixXd vertices = MapMatrixXfUnaligned(its.vertices.front().data(), Eigen::Index(its.vertices.size()), 3).cast<double>();
+        Eigen::MatrixXi indices = MapMatrixXiUnaligned(its.indices.front().data(), Eigen::Index(its.indices.size()), 3);
+        Eigen::MatrixXd corner_normals;
+        igl::per_corner_normals(vertices, indices, 5.0, corner_normals);
+
+        unsigned int vertices_counter = 0;
+        for (uint32_t i = 0; i < its.indices.size(); ++i) {
+            const stl_triangle_vertex_indices face = its.indices[i];
+            for (size_t j = 0; j < 3; ++j) {
+                const Vec3f normal = corner_normals.row(Eigen::Index(i * 3 + j)).cast<float>();
+                data.add_vertex(its.vertices[face[j]], normal);
+            }
+            data.add_triangle(vertices_counter, vertices_counter + 1, vertices_counter + 2);
+            vertices_counter += 3;
+        }
+    } else {
+        //Original flat (per-face) normals
+        unsigned int vertices_counter = 0;
+        for (uint32_t i = 0; i < its.indices.size(); ++i) {
+            const stl_triangle_vertex_indices face = its.indices[i];
+            const stl_vertex vertex[3] = {its.vertices[face[0]], its.vertices[face[1]], its.vertices[face[2]]};
+            const stl_vertex n = face_normal_normalized(vertex);
+            for (size_t j = 0; j < 3; ++j)
+                data.add_vertex(vertex[j], n);
+            data.add_triangle(vertices_counter, vertices_counter + 1, vertices_counter + 2);
+            vertices_counter += 3;
         }
-        vertices_counter += 3;
-        data.add_triangle(vertices_counter - 3, vertices_counter - 2, vertices_counter - 1);
     }
 
     // update bounding box

src/slic3r/GUI/Preferences.cpp

@@ -1578,6 +1578,15 @@ void PreferencesDialog::create_items()
     );
     g_sizer->Add(item_realistic_shadows);
 
+   
+    auto item_realistic_smooth_normals = create_item_checkbox(
+        _L("Smooth normals"),
+        _L("Applies smooth normals to the realistic view.\n\nRequires manual scene reload to take effect "
+                                "(right-click on 3D view → \"Reload All\")."),
+        SETTING_OPENGL_PHONG_SMOOTH_NORMALS
+    );
+    g_sizer->Add(item_realistic_smooth_normals);
+
     //// GRAPHICS > Anti-aliasing
     g_sizer->Add(create_item_title(_L("Anti-aliasing")), 1, wxEXPAND);
 

version.inc

@@ -7,7 +7,7 @@ set(SLIC3R_APP_KEY "OrcaSlicer")
 if(NOT DEFINED BBL_INTERNAL_TESTING)
 set(BBL_INTERNAL_TESTING "0")
 endif()
-set(SoftFever_VERSION "2.4.0-dev")
+set(SoftFever_VERSION "2.4.0")
 string(REGEX MATCH "^([0-9]+)\\.([0-9]+)\\.([0-9]+)"
        SoftFever_VERSION_MATCH ${SoftFever_VERSION})
 set(ORCA_VERSION_MAJOR ${CMAKE_MATCH_1})