feat: GLTF/GLB export with normals + B-Rep tessellation + pipeline example

examples/07_pipeline/CMakeLists.txt

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+add_executable(pipeline_demo main.cpp)
+target_link_libraries(pipeline_demo PRIVATE vde)

examples/07_pipeline/main.cpp

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+#include "vde/sdf/sdf_primitives.h"
+#include "vde/sdf/sdf_operations.h"
+#include "vde/sdf/sdf_to_mesh.h"
+#include "vde/brep/modeling.h"
+#include "vde/mesh/marching_cubes.h"
+#include "vde/mesh/halfedge_mesh.h"
+#include "vde/foundation/io_gltf.h"
+#include <iostream>
+#include <cmath>
+
+int main() {
+    // ── Pipeline 1: SDF → Mesh → GLB ──
+    std::cout << "Pipeline 1: SDF → Mesh → GLB\n";
+
+    // Build SDF expression: smooth union of sphere and box
+    auto sphere_sdf = [](const vde::core::Point3D& p) {
+        return vde::sdf::sphere(p, 1.5);
+    };
+
+    auto combined = [&](double x, double y, double z) -> double {
+        vde::core::Point3D p(x, y, z);
+        double d_sphere = sphere_sdf(p);
+        double d_box = vde::sdf::box(p, vde::core::Point3D(1.0, 1.0, 1.0));
+        return vde::sdf::op_smooth_union(d_sphere, d_box, 0.3);
+    };
+
+    // Marching cubes → MCMesh
+    double iso = 0.0;
+    vde::core::Point3D bmin(-3.0, -3.0, -3.0);
+    vde::core::Point3D bmax(3.0, 3.0, 3.0);
+    int resolution = 64;
+
+    auto mc_result = vde::mesh::marching_cubes(combined, iso, bmin, bmax, resolution);
+
+    // Build HalfedgeMesh from marching cubes result
+    vde::mesh::HalfedgeMesh sdf_mesh;
+    sdf_mesh.build_from_triangles(mc_result.vertices, mc_result.triangles);
+
+    // Export
+    vde::foundation::GltfOptions opt;
+    opt.binary = true;
+    opt.include_normals = true;
+
+    std::string sdf_out = "output_sdf_shape.glb";
+    if (vde::foundation::write_gltf(sdf_out, sdf_mesh, opt)) {
+        std::cout << "  → " << sdf_out << " written ("
+                  << sdf_mesh.num_vertices() << " vertices, "
+                  << sdf_mesh.num_faces() << " faces)\n";
+    } else {
+        std::cerr << "  ✗ Failed to write " << sdf_out << "\n";
+    }
+
+    // ── Pipeline 2: B-Rep → Tessellate → GLB ──
+    std::cout << "\nPipeline 2: B-Rep → Tessellate → GLB\n";
+
+    auto box_b = vde::brep::make_box(2.0, 2.0, 2.0);
+    auto shelled = vde::brep::shell(box_b, -1, 0.15);  // closed shell, 0.15 thickness
+
+    std::string brep_out = "output_brep_shell.glb";
+    if (vde::foundation::write_brep_gltf(brep_out, shelled, 32)) {
+        std::cout << "  → " << brep_out << " written\n";
+    } else {
+        std::cerr << "  ✗ Failed to write " << brep_out << "\n";
+    }
+
+    std::cout << "\nDone! Open .glb files in any 3D viewer.\n";
+    return 0;
+}