feat: LOD mesh generation + incremental BVH

2026-07-24 16:14:09 +00:00
parent 5a2f01f597
commit e02c5980b4
7 changed files with 455 additions and 0 deletions
@@ -3,3 +3,4 @@ add_vde_test(test_delaunay)
 add_vde_test(test_quality)
 add_vde_test(test_smooth)
 add_vde_test(test_delaunay_3d)
+add_vde_test(test_mesh_lod)
@@ -0,0 +1,151 @@
+#include <gtest/gtest.h>
+#include "vde/mesh/mesh_lod.h"
+#include "vde/mesh/halfedge_mesh.h"
+#include <cmath>
+
+using namespace vde::mesh;
+
+/// Create a simple box mesh (12 triangles, 8 vertices)
+static HalfedgeMesh make_box_mesh() {
+    // Unit cube vertices
+    std::vector<Point3D> verts = {
+        {0, 0, 0}, {1, 0, 0}, {1, 1, 0}, {0, 1, 0},  // bottom
+        {0, 0, 1}, {1, 0, 1}, {1, 1, 1}, {0, 1, 1},  // top
+    };
+    // 12 triangles (2 per face)
+    std::vector<std::array<int, 3>> tris = {
+        {0, 2, 1}, {0, 3, 2},   // front
+        {1, 2, 6}, {1, 6, 5},   // right
+        {5, 6, 7}, {5, 7, 4},   // back
+        {4, 7, 3}, {4, 3, 0},   // left
+        {3, 7, 6}, {3, 6, 2},   // top
+        {4, 0, 1}, {4, 1, 5},   // bottom
+    };
+
+    HalfedgeMesh mesh;
+    mesh.build_from_triangles(verts, tris);
+    return mesh;
+}
+
+// ──────────────────────────────────────────────────────
+//  LOD generation
+// ──────────────────────────────────────────────────────
+
+TEST(LODMeshTest, GenerateLOD_DefaultLevels) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    // Default: 3 levels (base + 2 simplified)
+    EXPECT_EQ(lod.levels.size(), 3u);
+    EXPECT_EQ(lod.thresholds.size(), 3u);
+
+    // Level 0 is the original mesh (12 faces)
+    EXPECT_GE(lod.levels[0].num_faces(), 8u);
+    // Each level should have ≤ faces than previous
+    EXPECT_LE(lod.levels[1].num_faces(), lod.levels[0].num_faces());
+    EXPECT_LE(lod.levels[2].num_faces(), lod.levels[1].num_faces());
+}
+
+TEST(LODMeshTest, GenerateLOD_SingleLevel) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 1, 0.5);
+
+    // Only 1 level = base (no simplification)
+    EXPECT_EQ(lod.levels.size(), 1u);
+    EXPECT_EQ(lod.levels[0].num_faces(), 12u);
+}
+
+TEST(LODMeshTest, GenerateLOD_AggressiveReduction) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 5, 0.1);  // keep only 10% each level
+
+    // Should stop early when < 4 faces remain
+    EXPECT_GE(lod.levels.size(), 1u);
+    EXPECT_LE(lod.levels.size(), 5u);
+}
+
+TEST(LODMeshTest, GenerateLOD_EmptyMesh) {
+    HalfedgeMesh empty;
+    auto lod = generate_lod(empty, 3, 0.5);
+
+    EXPECT_EQ(lod.levels.size(), 1u);  // only base
+    EXPECT_EQ(lod.levels[0].num_faces(), 0u);
+}
+
+// ──────────────────────────────────────────────────────
+//  level_for_error
+// ──────────────────────────────────────────────────────
+
+TEST(LODMeshTest, LevelForError_ZeroError) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    // error 0 → base level (threshold 0.0)
+    EXPECT_EQ(lod.level_for_error(0.0), 0);
+}
+
+TEST(LODMeshTest, LevelForError_ThresholdBoundary) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    // thresholds: [0.0, 100.0, 200.0]
+    EXPECT_EQ(lod.level_for_error(50.0), 0);
+    EXPECT_EQ(lod.level_for_error(100.0), 1);   // ≥ 100 → level 1
+    EXPECT_EQ(lod.level_for_error(150.0), 1);
+    EXPECT_EQ(lod.level_for_error(200.0), 2);   // ≥ 200 → level 2
+    EXPECT_EQ(lod.level_for_error(999.0), 2);
+}
+
+TEST(LODMeshTest, LevelForError_NegativeError) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    // Negative error → level 0 (base)
+    EXPECT_EQ(lod.level_for_error(-1.0), 0);
+}
+
+// ──────────────────────────────────────────────────────
+//  mesh_at
+// ──────────────────────────────────────────────────────
+
+TEST(LODMeshTest, MeshAt_ValidLevels) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    EXPECT_EQ(lod.mesh_at(0).num_faces(), 12u);
+    EXPECT_LE(lod.mesh_at(1).num_faces(), 12u);
+    EXPECT_LE(lod.mesh_at(2).num_faces(), lod.mesh_at(1).num_faces());
+}
+
+TEST(LODMeshTest, MeshAt_ClampNegative) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    // Negative level → clamped to 0
+    EXPECT_EQ(lod.mesh_at(-1).num_faces(), lod.mesh_at(0).num_faces());
+    EXPECT_EQ(lod.mesh_at(-100).num_faces(), lod.mesh_at(0).num_faces());
+}
+
+TEST(LODMeshTest, MeshAt_ClampTooHigh) {
+    auto box = make_box_mesh();
+    auto lod = generate_lod(box, 3, 0.5);
+
+    int last = static_cast<int>(lod.levels.size()) - 1;
+    EXPECT_EQ(lod.mesh_at(999).num_faces(), lod.mesh_at(last).num_faces());
+}
+
+TEST(LODMeshTest, MeshAt_EmptyLOD) {
+    LODMesh empty_lod;
+    // mesh_at returns a static empty mesh for empty LOD
+    EXPECT_EQ(empty_lod.mesh_at(0).num_faces(), 0u);
+    EXPECT_EQ(empty_lod.mesh_at(5).num_faces(), 0u);
+}
+
+// ──────────────────────────────────────────────────────
+//  generate_brep_lod (integration)
+// ──────────────────────────────────────────────────────
+
+// Forward-declare for linking only (no brep::make_box in this TU's link deps)
+// This test is compile-time only; runtime needs brep linked.
+// We test through the LOD API directly above; brep path is tested
+// in the brep test suite.