ViewDesignEngine/tests/mesh/test_quality.cpp

#include <gtest/gtest.h>
#include "vde/mesh/mesh_quality.h"
#include "vde/mesh/halfedge_mesh.h"

using namespace vde::mesh;

TEST(MeshQualityTest, EquilateralTriangle_PerfectQuality) {
    HalfedgeMesh mesh;
    // Equilateral triangle side length ≈ 1.155 for area ≈ 0.577
    double h = std::sqrt(3.0) / 2.0;
    mesh.build_from_triangles(
        {Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(0.5, h, 0)},
        {{0, 1, 2}}
    );

    auto q = evaluate_mesh_quality(mesh);

    // Equilateral triangle: all angles = 60°
    EXPECT_NEAR(q.min_angle_deg, 60.0, 1.0);
    EXPECT_NEAR(q.max_angle_deg, 60.0, 1.0);
    // Aspect ratio ~1 for equilateral
    EXPECT_NEAR(q.avg_aspect_ratio, 1.0, 0.1);
    EXPECT_EQ(q.degenerate_faces, 0u);
}

TEST(MeshQualityTest, DegenerateTriangle_ZeroArea) {
    HalfedgeMesh mesh;
    // Collinear points → zero area
    mesh.build_from_triangles(
        {Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(2, 0, 0)},
        {{0, 1, 2}}
    );

    auto q = evaluate_mesh_quality(mesh);
    EXPECT_EQ(q.degenerate_faces, 1u);
}

TEST(MeshQualityTest, ObtuseTriangle_LargeMaxAngle) {
    HalfedgeMesh mesh;
    // Very flat obtuse triangle: (0,0), (10,0), (0,0.1)
    mesh.build_from_triangles(
        {Point3D(0, 0, 0), Point3D(10, 0, 0), Point3D(0, 0.1, 0)},
        {{0, 1, 2}}
    );

    auto q = evaluate_mesh_quality(mesh);
    // Max angle should be very close to 180 (or at least > 90)
    EXPECT_GT(q.max_angle_deg, 90.0);
    // Min angle should be very small
    EXPECT_LT(q.min_angle_deg, 10.0);
}

TEST(MeshQualityTest, RightTriangle) {
    HalfedgeMesh mesh;
    // 3-4-5 right triangle
    mesh.build_from_triangles(
        {Point3D(0, 0, 0), Point3D(3, 0, 0), Point3D(0, 4, 0)},
        {{0, 1, 2}}
    );

    auto q = evaluate_mesh_quality(mesh);
    // Right triangle: one angle ~90°, others ~36.87° and ~53.13°
    EXPECT_NEAR(q.max_angle_deg, 90.0, 2.0);
    EXPECT_GT(q.min_angle_deg, 30.0);
    EXPECT_EQ(q.degenerate_faces, 0u);
}

TEST(MeshQualityTest, MultipleTriangles_Mixed) {
    HalfedgeMesh mesh;
    // Two triangles: one good, one degenerate
    double h = std::sqrt(3.0) / 2.0;
    mesh.build_from_triangles(
        {
            Point3D(0, 0, 0), Point3D(1, 0, 0), Point3D(0.5, h, 0),    // equilateral
            Point3D(10, 0, 0), Point3D(11, 0, 0), Point3D(12, 0, 0),   // degenerate
        },
        {{0, 1, 2}, {3, 4, 5}}
    );

    auto q = evaluate_mesh_quality(mesh);
    EXPECT_EQ(q.degenerate_faces, 1u);
    // Average aspect ratio should reflect the mix
    EXPECT_GT(q.avg_aspect_ratio, 0.5); // mixed quality, should be > 0.5
}

TEST(MeshQualityTest, EmptyMesh) {
    HalfedgeMesh mesh;
    auto q = evaluate_mesh_quality(mesh);
    EXPECT_EQ(q.degenerate_faces, 0u);
    // Default values for empty mesh
    EXPECT_DOUBLE_EQ(q.min_angle_deg, 0.0);
    EXPECT_DOUBLE_EQ(q.max_angle_deg, 0.0);
}

TEST(MeshQualityTest, HighAspectRatioTriangle) {
    HalfedgeMesh mesh;
    // Very thin triangle
    mesh.build_from_triangles(
        {Point3D(0, 0, 0), Point3D(100, 0, 0), Point3D(0, 0.01, 0)},
        {{0, 1, 2}}
    );

    auto q = evaluate_mesh_quality(mesh);
    // Aspect ratio should be very high
    EXPECT_GT(q.max_aspect_ratio, 10.0);
}