Give OBJ Quad and Flipped Faces the Texture Coordinates of Their Own Corners

load_obj emits the second triangle of a quad from corners 0, 2 and 3,
but read its texture coordinates from corners 0, 1 and 2, so half of
every textured quad sampled the wrong part of the texture. The corner
indices are now passed down to where the coordinates are read.

A mesh with inward-facing triangles is flipped after loading, which
swaps corners 1 and 2 of every face. The texture coordinates were left
as they were. They are now swapped along with the corners.

.github/workflows/unit_tests.yml

@@ -44,14 +44,6 @@ jobs:
         uses: actions/download-artifact@v8
         with:
           name: ${{ inputs.artifact }}
-      # run_unit_tests.sh installs the plugin tests' numpy with the uv the build stages
-      # beside them; the Windows arm64 build bundles none, so put one on PATH there.
-      - name: Install uv
-        if: runner.os == 'Windows' && runner.arch == 'ARM64'
-        uses: astral-sh/setup-uv@v10.2.0
-        with:
-          version: "0.11.21"  # ORCA_UV_VERSION in CMakeLists.txt
-          enable-cache: false
       - uses: lukka/get-cmake@latest
         with:
           cmakeVersion: "~4.3.0"  # use most recent 4.3.x version

.gitignore

@@ -52,6 +52,4 @@ internal_docs/
 __pycache__/
 *.pyc
 *.opc
-/.test/
-docs/superpowers/
-ctest_results.xml
+docs/superpowers/

scripts/run_unit_tests.sh

@@ -2,8 +2,7 @@
 
 # This file is made to support the unit tests workflow.
 # It should only require the directories build/tests, scripts/, and tests/ to function,
-# and cmake (with ctest) installed -- plus network access to PyPI whenever numpy has to
-# be installed into a freshly built test tree (see below).
+# and cmake (with ctest) installed.
 # (otherwise, update the workflow too, but try to avoid to keep things self-contained)
 #
 # Usage: run_unit_tests.sh [TEST_DIR] [BUILD_CONFIG]
@@ -19,52 +18,6 @@ cd "${ROOT_DIR}" || exit 1
 TEST_DIR="${1:-build/tests}"
 BUILD_CONFIG="${2:-}"
 
-# The slic3rutils plugin-host tests build numpy arrays through the CPython copied next
-# to the test binary (see tests/slic3rutils/CMakeLists.txt), which ships no numpy.
-# Install it with the uv staged beside that runtime -- the tool the app installs plugin
-# dependencies with -- straight into the interpreter's own site-packages: no pip needed
-# in the runtime, no PYTHONPATH. Re-checked every run because a rebuild of the test
-# target re-copies the runtime; needs network whenever it installs. Pinned so a numpy
-# release cannot change results on its own.
-NUMPY_VERSION="2.5.3"
-
-# Without numpy those tests assert the numpy-absent error path instead, so a local run
-# only warns. Under CI it fails the run, which would otherwise stay green while silently
-# dropping the array coverage. (The Flatpak leg runs this inside `flatpak build`, whose
-# minimal environment has no CI, and its offline build stages no uv, so numpy stays
-# best-effort there.)
-numpy_unavailable() {
-    if [ -n "${CI:-}" ]; then
-        echo "error: $1" >&2
-        exit 1
-    fi
-    echo "warning: $1; the numpy-backed binding tests will cover only the numpy-absent path."
-}
-
-has_pinned_numpy() {
-    "${python_exe}" -c "import sys, numpy; sys.exit(numpy.__version__ != '${NUMPY_VERSION}')" >/dev/null 2>&1
-}
-
-find_args=("${TEST_DIR}" \( -path '*/python/bin/python3' -o -path '*/python/python.exe' \))
-# Multi-config trees hold one copy per configuration; only bootstrap the one being run.
-[ -n "${BUILD_CONFIG}" ] && find_args+=(-path "*/${BUILD_CONFIG}/*")
-python_exe="$(find "${find_args[@]}" -print -quit 2>/dev/null)"
-
-if [ -z "${python_exe}" ]; then
-    numpy_unavailable "no bundled Python under ${TEST_DIR}"
-elif ! has_pinned_numpy; then
-    uv_exe="${python_exe%/python/*}/tools/uv/uv"
-    # Builds that bundle no uv (Windows arm64) fall back to one on PATH.
-    [ -x "${uv_exe}" ] || uv_exe="$(command -v uv)"
-    echo "Installing numpy ${NUMPY_VERSION} into the embedded test interpreter (${python_exe})..."
-    if [ -z "${uv_exe}" ]; then
-        numpy_unavailable "no uv staged beside the tests or on PATH"
-    elif ! "${uv_exe}" pip install --python "${python_exe}" --only-binary :all: "numpy==${NUMPY_VERSION}" \
-            || ! has_pinned_numpy; then
-        numpy_unavailable "could not install numpy ${NUMPY_VERSION} into ${python_exe}"
-    fi
-fi
-
 # Run the whole suite, excluding tests tagged [NotWorking] and tests labelled RequiresApp,
 # which run the built orca-slicer binary that this directory does not contain.
 # --no-tests=error fails the job if the filter matches nothing (instead of passing green).

src/libslic3r/Format/OBJ.cpp

@@ -141,7 +141,7 @@ bool load_obj(const char *path, TriangleMesh *meshptr, ObjInfo& obj_info, std::s
                 its.indices.emplace_back(indices[0], indices[1], indices[2]);
                 int  face_index =its.indices.size() - 1;
                 RGBA face_color;
-                auto set_face_color = [&uvs, &data, &mtl_data, &obj_info, &face_color](int face_index, const std::string mtl_name) {
+                auto set_face_color = [&uvs, &data, &mtl_data, &obj_info, &face_color](int face_index, const std::string mtl_name, const std::array<int, 3> &corners) {
                     if (mtl_data.new_mtl_unmap.find(mtl_name) != mtl_data.new_mtl_unmap.end()) {
                         bool is_merge_ka_kd = true;
                         for (size_t n = 0; n < 3; n++) {
@@ -174,7 +174,7 @@ bool load_obj(const char *path, TriangleMesh *meshptr, ObjInfo& obj_info, std::s
                                     return Vec2f::Zero();
                                 return Vec2f(data.textureCoordinates[idx * OBJ_TEXCOORD_LENGTH], data.textureCoordinates[idx * OBJ_TEXCOORD_LENGTH + 1]);
                             };
-                            std::array<Vec2f, 3> uv_array{uv_at(uvs[0]), uv_at(uvs[1]), uv_at(uvs[2])};
+                            std::array<Vec2f, 3> uv_array{uv_at(uvs[corners[0]]), uv_at(uvs[corners[1]]), uv_at(uvs[corners[2]])};
                             obj_info.uvs.emplace_back(uv_array);
                         }
                         obj_info.face_colors.emplace_back(face_color);
@@ -185,27 +185,27 @@ bool load_obj(const char *path, TriangleMesh *meshptr, ObjInfo& obj_info, std::s
                         }
                     }
                 };
-                auto set_face_color_by_mtl = [&data, &set_face_color](int face_index) {
+                auto set_face_color_by_mtl = [&data, &set_face_color](int face_index, const std::array<int, 3> &corners) {
                     if (data.usemtls.size() == 1) {
-                        set_face_color(face_index, data.usemtls[0].name);
+                        set_face_color(face_index, data.usemtls[0].name, corners);
                     } else {
                         for (size_t k = 0; k < data.usemtls.size(); k++) {
                             auto mtl = data.usemtls[k];
                             if (face_index >= mtl.face_start && face_index <= mtl.face_end) {
-                                set_face_color(face_index, data.usemtls[k].name);
+                                set_face_color(face_index, data.usemtls[k].name, corners);
                                 break;
                             }
                         }
                     }
                 };
                 if (exist_mtl) {
-                    set_face_color_by_mtl(face_index);
+                    set_face_color_by_mtl(face_index, {0, 1, 2});
                 }
                 if (cnt == 4) {
                     its.indices.emplace_back(indices[0], indices[2], indices[3]);
                     int face_index = its.indices.size() - 1;
                     if (exist_mtl) {
-                        set_face_color_by_mtl(face_index);
+                        set_face_color_by_mtl(face_index, {0, 2, 3});
                     }
                 }
             }
@@ -217,8 +217,12 @@ bool load_obj(const char *path, TriangleMesh *meshptr, ObjInfo& obj_info, std::s
         message = _L("This OBJ file couldn't be read because it's empty.");
         return false;
     }
-    if (meshptr->volume() < 0)
+    if (meshptr->volume() < 0) {
         meshptr->flip_triangles();
+        // Flipping swaps corners 1 and 2 of every face, so the UVs have to follow.
+        for (std::array<Vec2f, 3> &uv : obj_info.uvs)
+            std::swap(uv[1], uv[2]);
+    }
     // Hand the parsed material table back so callers can build a TexturedMesh from it.
     if (out_mtl)
         *out_mtl = mtl_data;

src/slic3r/CMakeLists.txt

@@ -1019,9 +1019,14 @@ if (UNIX AND NOT APPLE)
     find_package(GTK${SLIC3R_GTK} REQUIRED)
     pkg_check_modules(LIBSECRET REQUIRED libsecret-1)
     pkg_check_modules(webkit2gtk REQUIRED webkit2gtk-4.1)
-    find_package(X11 REQUIRED)
+    if (FLATPAK)
+        # I don't know why this is needed, but for whatever reason slic3r isn't
+        # linking to X11 and webkit2gtk. force it.
+        find_package(X11 REQUIRED)
+        target_link_libraries(libslic3r_gui ${X11_LIBRARIES} ${webkit2gtk_LIBRARIES})
+    endif()
     target_include_directories(libslic3r_gui SYSTEM PRIVATE ${GTK${SLIC3R_GTK}_INCLUDE_DIRS} ${LIBSECRET_INCLUDE_DIRS} ${webkit2gtk_INCLUDE_DIRS})
-    target_link_libraries(libslic3r_gui ${GTK${SLIC3R_GTK}_LIBRARIES} fontconfig ${LIBSECRET_LIBRARIES} ${webkit2gtk_LIBRARIES} ${X11_LIBRARIES})
+    target_link_libraries(libslic3r_gui ${GTK${SLIC3R_GTK}_LIBRARIES} fontconfig ${LIBSECRET_LIBRARIES})
 
     # Propagate GDK backend detection results as compile definitions so that
     # LinuxDisplayBackend.cpp can include the right GDK headers.

src/slic3r/plugin/PythonInterpreter.cpp

@@ -345,21 +345,16 @@ boost::filesystem::path find_bundled_python_home()
     fs::path bundle_python = fs::path(resources_dir()).parent_path() / "MacOS" / "python";
     if (valid_python_home(bundle_python))
         return bundle_python;
-#elif !defined(_WIN32)
+#elif defined(_WIN32)
+    fs::path exe_python = boost::dll::program_location().parent_path() / "python";
+    if (valid_python_home(exe_python))
+        return exe_python;
+#else
     fs::path linux_python = fs::path(resources_dir()).parent_path() / "lib" / "python";
     if (valid_python_home(linux_python))
         return linux_python;
 #endif
 
-    // Next to the executable: the Windows install layout, and the runtime copied
-    // beside every platform's unit-test binary (tests/slic3rutils/CMakeLists.txt).
-    // The CI test runner only receives the build/tests tree, so the candidates
-    // below -- all of which point into the deps or install trees -- never resolve
-    // there.
-    fs::path exe_python = boost::dll::program_location().parent_path() / "python";
-    if (valid_python_home(exe_python))
-        return exe_python;
-
     fs::path configured_python = ORCA_BUNDLED_PYTHON_ROOT;
     if (!configured_python.empty() && valid_python_home(configured_python))
         return configured_python;

tests/libslic3r/test_obj.cpp

@@ -19,9 +19,8 @@ struct LoadedObj
     ObjInfo      info;
 };
 
-// A tetrahedron with a material and two texture coordinates, (0.25, 0.5) and (0.75, 1).
-// Only the first face and the vt lines are varied; the other three faces reference vt 1.
-LoadedObj load_textured_tetrahedron(const std::string &first_face, const std::string &vts = "vt 0.25 0.5\nvt 0.75 1\n")
+// Loads an OBJ made of the given lines, with a material library that defines material "a".
+LoadedObj load_textured_obj(const std::string &body)
 {
     ScopedTemporaryFile obj(".obj");
     ScopedTemporaryFile mtl(".mtl");
@@ -31,12 +30,7 @@ LoadedObj load_textured_tetrahedron(const std::string &first_face, const std::st
     }
     {
         boost::nowide::ofstream out(obj.string());
-        out << "mtllib " << mtl.path().filename().string() << "\n"
-            << "v 0 0 0\nv 10 0 0\nv 0 10 0\nv 0 0 10\n"
-            << vts
-            << "usemtl a\n"
-            << first_face << "\n"
-            << "f 1/1 2/1 4/1\nf 1/1 4/1 3/1\nf 2/1 3/1 4/1\n";
+        out << "mtllib " << mtl.path().filename().string() << "\n" << body;
     }
     LoadedObj   loaded;
     std::string message;
@@ -44,6 +38,21 @@ LoadedObj load_textured_tetrahedron(const std::string &first_face, const std::st
     return loaded;
 }
 
+// A tetrahedron with a material and two texture coordinates, (0.25, 0.5) and (0.75, 1).
+// Only the first face and the vt lines are varied; the other three faces reference vt 1.
+LoadedObj load_textured_tetrahedron(const std::string &first_face, const std::string &vts = "vt 0.25 0.5\nvt 0.75 1\n")
+{
+    return load_textured_obj("v 0 0 0\nv 10 0 0\nv 0 10 0\nv 0 0 10\n" + vts + "usemtl a\n" + first_face + "\n" +
+                             "f 1/1 2/1 4/1\nf 1/1 4/1 3/1\nf 2/1 3/1 4/1\n");
+}
+
+// Texture coordinate n is (n / 10, n / 20), so a UV identifies the vt it came from.
+void check_uv_is_vt(const Vec2f &uv, int vt)
+{
+    CHECK_THAT(uv.x(), WithinAbs(vt / 10., 1e-6));
+    CHECK_THAT(uv.y(), WithinAbs(vt / 20., 1e-6));
+}
+
 } // namespace
 
 TEST_CASE("An out-of-range texture index falls back to a zero UV and keeps the geometry", "[OBJ][Regression]")
@@ -120,3 +129,39 @@ TEST_CASE("A texture coordinate with w does not shift the indices of the ones af
     CHECK_THAT(uv[2].x(), WithinAbs(0.75, 1e-6));
     CHECK_THAT(uv[2].y(), WithinAbs(1., 1e-6));
 }
+
+TEST_CASE("Both triangles of a quad take the texture coordinates of their own corners", "[OBJ][Regression]")
+{
+    const LoadedObj loaded = load_textured_obj("v 0 0 0\nv 10 0 0\nv 10 10 0\nv 0 10 0\n"
+                                               "vt 0.1 0.05\nvt 0.2 0.1\nvt 0.3 0.15\nvt 0.4 0.2\n"
+                                               "usemtl a\n"
+                                               "f 1/1 2/2 3/3 4/4\n");
+
+    REQUIRE(loaded.ok);
+    REQUIRE(loaded.mesh.facets_count() == 2);
+    REQUIRE(loaded.info.uvs.size() == 2);
+    check_uv_is_vt(loaded.info.uvs[0][0], 1);
+    check_uv_is_vt(loaded.info.uvs[0][1], 2);
+    check_uv_is_vt(loaded.info.uvs[0][2], 3);
+    check_uv_is_vt(loaded.info.uvs[1][0], 1);
+    check_uv_is_vt(loaded.info.uvs[1][1], 3);
+    check_uv_is_vt(loaded.info.uvs[1][2], 4);
+}
+
+TEST_CASE("Texture coordinates follow the corners of a mesh that is flipped on load", "[OBJ][Regression]")
+{
+    // The faces wind inwards, so the loader flips them. Vertex n uses vt n.
+    const LoadedObj loaded = load_textured_obj("v 0 0 0\nv 10 0 0\nv 0 10 0\nv 0 0 10\n"
+                                               "vt 0.1 0.05\nvt 0.2 0.1\nvt 0.3 0.15\nvt 0.4 0.2\n"
+                                               "usemtl a\n"
+                                               "f 1/1 2/2 3/3\nf 1/1 4/4 2/2\nf 1/1 3/3 4/4\nf 2/2 4/4 3/3\n");
+
+    REQUIRE(loaded.ok);
+    const indexed_triangle_set &its = loaded.mesh.its;
+    CHECK(its_volume(its) > 0.f);
+    REQUIRE(its.indices.size() == 4);
+    REQUIRE(loaded.info.uvs.size() == 4);
+    for (size_t face = 0; face < its.indices.size(); ++face)
+        for (int corner = 0; corner < 3; ++corner)
+            check_uv_is_vt(loaded.info.uvs[face][corner], its.indices[face][corner] + 1);
+}

tests/slic3rutils/CMakeLists.txt

@@ -51,16 +51,9 @@ if (WIN32)
         COMMENT "Copying Python runtime for slic3rutils plugin host API tests"
         VERBATIM
     )
-elseif (NOT FLATPAK)
-    # The CI unit-test runner only receives the build/tests tree, so both the
-    # interpreter and the libpython the test binary links have to travel next to
-    # the executable; find_bundled_python_home() picks the copy up from there.
-    if (APPLE)
-        target_link_options(${_TEST_NAME}_tests PRIVATE
-            "LINKER:-rpath,@executable_path/python/lib")
-    else ()
-        set_property(TARGET ${_TEST_NAME}_tests APPEND PROPERTY BUILD_RPATH "$ORIGIN/python/lib")
-    endif ()
+elseif (APPLE)
+    target_link_options(${_TEST_NAME}_tests PRIVATE
+        "LINKER:-rpath,@executable_path/python/lib")
 
     add_custom_command(TARGET ${_TEST_NAME}_tests POST_BUILD
         COMMAND ${CMAKE_COMMAND} -E rm -rf
@@ -68,7 +61,7 @@ elseif (NOT FLATPAK)
         COMMAND ${CMAKE_COMMAND} -E copy_directory
             "${CMAKE_PREFIX_PATH}/libpython"
             "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/python"
-        COMMENT "Copying Python runtime for the plugin host API tests"
+        COMMENT "Copying Python runtime for macOS plugin host API tests"
         VERBATIM
     )
 elseif (FLATPAK)
@@ -85,16 +78,4 @@ elseif (FLATPAK)
     )
 endif()
 
-# scripts/run_unit_tests.sh installs the tests' numpy into that runtime with this uv,
-# staged where the app build tree keeps it (<exe dir>/tools/uv, see src/CMakeLists.txt).
-if (ORCA_BUNDLED_UV_EXECUTABLE)
-    add_custom_command(TARGET ${_TEST_NAME}_tests POST_BUILD
-        COMMAND ${CMAKE_COMMAND} -E make_directory "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/tools/uv"
-        COMMAND ${CMAKE_COMMAND} -E copy_if_different "${ORCA_BUNDLED_UV_EXECUTABLE}"
-            "$<TARGET_FILE_DIR:${_TEST_NAME}_tests>/tools/uv/${ORCA_BUNDLED_UV_FILENAME}"
-        COMMENT "Copying uv for the plugin host API tests"
-        VERBATIM
-    )
-endif()
-
 orcaslicer_discover_tests(${_TEST_NAME}_tests)