Add tests for SupportSpotsGenerator::ObjectPart construction.

Ensuring that ObjectParts in SupportSpotsGenerator are properly
generated from slice is crucial for any further computations.

src/libslic3r/SupportSpotsGenerator.cpp

@@ -478,11 +478,11 @@ ObjectPart::ObjectPart(
         const Integrals integrals{polygons};
         const float volume = integrals.area * layer_height;
         this->volume += volume;
-        this->volume_centroid_accumulator += to_3d(integrals.x_i, center_z * integrals.area) / integrals.area * volume; // TODO check that it is correct
+        this->volume_centroid_accumulator += to_3d(integrals.x_i, center_z * integrals.area) / integrals.area * volume;
 
         if (this->connected_to_bed) {
             this->sticking_area += integrals.area;
-            this->sticking_centroid_accumulator += to_3d(integrals.x_i, bottom_z * integrals.area); // TODO check that it layer height should be added
+            this->sticking_centroid_accumulator += to_3d(integrals.x_i, bottom_z * integrals.area);
             this->sticking_second_moment_of_area_accumulator += integrals.x_i_squared;
             this->sticking_second_moment_of_area_covariance_accumulator += integrals.xy;
         }

src/libslic3r/SupportSpotsGenerator.hpp

@@ -208,6 +208,8 @@ struct SliceConnection
     void print_info(const std::string &tag) const;
 };
 
+Polygons get_brim(const ExPolygon& slice_polygon, const BrimType brim_type, const float brim_width);
+
 class ObjectPart
 {
 public:

tests/libslic3r/test_support_spots_generator.cpp

@@ -96,23 +96,70 @@ TEST_CASE("Moments calculation for rotated axis.", "[SupportSpotsGenerator]") {
     CHECK(moment_calculated_then_rotated == Approx(moment_rotated_polygon));
 }
 
-TEST_CASE("TODO", "[SupportSpotsGenerator]") {
+struct ObjectPartFixture {
     const Polyline polyline{
         Point{scaled(Vec2f{0, 0})},
         Point{scaled(Vec2f{1, 0})},
     };
+    const float width = 0.1f;
+    bool connected_to_bed = true;
+    coordf_t print_head_z = 0.2;
+    coordf_t layer_height = 0.2;
     ExtrusionAttributes attributes;
-    attributes.width = 0.1;
-    const ExtrusionPath path{polyline, attributes};
     ExtrusionEntityCollection collection;
-    collection.append(path);
+    std::vector<const ExtrusionEntityCollection*> extrusions{};
-    std::vector<const ExtrusionEntityCollection*> collections{&collection};
+    Polygon expected_polygon{
+        Point{scaled(Vec2f{0, -width / 2})},
+        Point{scaled(Vec2f{1, -width / 2})},
+        Point{scaled(Vec2f{1, width / 2})},
+        Point{scaled(Vec2f{0, width / 2})}
+    };
 
-    Polygons polygons = path.polygons_covered_by_width();
+    ObjectPartFixture() {
-    for (const Polygon& polygon : polygons) {
+        attributes.width = width;
-        std::cout << "Polygon: " << std::endl;
+        const ExtrusionPath path{polyline, attributes};
-        for (const Line& line : polygon.lines()) {
+        collection.append(path);
-            std::cout << "(" << line.a.x() << ", " << line.a.y() << ")" << std::endl;
+        extrusions.push_back(&collection);
     }
+};
+
+TEST_CASE_METHOD(ObjectPartFixture, "Constructing ObjectPart using extrusion collections", "[SupportSpotsGenerator]") {
+    ObjectPart part{
+        extrusions,
+        connected_to_bed,
+        print_head_z,
+        layer_height,
+        std::nullopt
+    };
+
+    Integrals expected{{expected_polygon}};
+
+    CHECK(part.connected_to_bed == true);
+    Vec3f volume_centroid{part.volume_centroid_accumulator / part.volume};
+    CHECK(volume_centroid.x() == Approx(0.5));
+    CHECK(volume_centroid.y() == Approx(0));
+    CHECK(volume_centroid.z() == Approx(layer_height / 2));
+    CHECK(part.sticking_area == Approx(expected.area));
+    CHECK(part.sticking_centroid_accumulator.x() == Approx(expected.x_i.x()));
+    CHECK(part.sticking_centroid_accumulator.y() == Approx(expected.x_i.y()));
+    CHECK(part.sticking_second_moment_of_area_accumulator.x() == Approx(expected.x_i_squared.x()));
+    CHECK(part.sticking_second_moment_of_area_accumulator.y() == Approx(expected.x_i_squared.y()));
+    CHECK(part.sticking_second_moment_of_area_covariance_accumulator == Approx(expected.xy).margin(1e-6));
+    CHECK(part.volume == Approx(layer_height * width));
 }
+
+TEST_CASE_METHOD(ObjectPartFixture, "Constructing ObjectPart with brim", "[SupportSpotsGenerator]") {
+    float brim_width = 1;
+    Polygons brim = get_brim(ExPolygon{expected_polygon}, BrimType::btOuterOnly, brim_width);
+
+    ObjectPart part{
+        extrusions,
+        connected_to_bed,
+        print_head_z,
+        layer_height,
+        brim
+    };
+
+    CHECK(part.sticking_area == Approx((1 + 2*brim_width) * (width + 2*brim_width)));
 }
+