Add 3D mesh generation examples

.gitignore

@@ -15,3 +15,9 @@ Cargo.lock
 
 # wasm-pack output
 pkg/
+
+# Generated example outputs
+examples/*.stl
+examples/*.obj
+examples/*.glb
+examples/*.vtk

README.md

@@ -113,6 +113,8 @@ let tetrahedra = surface_to_volume(8, 8, 8, min, max, &sphere, 0.0);
 
 ## Examples
 
+### 2D
+
 ```
 cargo run --example simple_2d_triangulation
 cargo run --example 2d_plot 100
@@ -123,6 +125,23 @@ cargo run --example 2d_plot 100
 ![10000points](examples/delaunay_2d_10000_points.png)
 ![100000points](examples/delaunay_2d_100000_points.png)
 
+### 3D
+
+```
+# Bowyer-Watson 3D on cube vertices
+cargo run --example simple_3d_tetrahedralization
+
+# Marching cubes sphere → export to STL, OBJ, GLB, VTK
+cargo run --example sphere_mesh_export
+
+# All pipeline algorithms (marching cubes, surface_to_volume, octree_refined, voxel_refined)
+cargo run --example pipeline_example
+```
+
+Output files are written to `examples/` and can be viewed with:
+- **STL/OBJ/GLB** - MeshLab, Blender, [glTF Viewer](https://gltf-viewer.donmccurdy.com/)
+- **VTK** - ParaView
+
 ## Benchmarks
 
 ```

examples/pipeline_example.rs

@@ -0,0 +1,85 @@
+use meshing::export::{faces_to_stl, tetrahedra_to_stl, tetrahedra_to_vtk};
+use meshing::marching_cubes::marching_cubes;
+use meshing::pipeline::{octree_refined, surface_to_volume, voxel_refined};
+use meshing::Point3D;
+use std::fs;
+
+fn main() {
+    let min = Point3D {
+        index: 0,
+        x: -2.0,
+        y: -2.0,
+        z: -2.0,
+    };
+    let max = Point3D {
+        index: 0,
+        x: 2.0,
+        y: 2.0,
+        z: 2.0,
+    };
+
+    // --- Marching Cubes: sphere isosurface ---
+    println!("=== Marching Cubes (sphere) ===");
+    let sphere = |x: f64, y: f64, z: f64| x * x + y * y + z * z - 1.0;
+    let faces = marching_cubes(15, 15, 15, min, max, &sphere, 0.0);
+    println!("  Faces: {}", faces.len());
+    let stl = faces_to_stl(&faces, "marching_cubes_sphere");
+    fs::write("examples/marching_cubes_sphere.stl", &stl).unwrap();
+    println!("  -> examples/marching_cubes_sphere.stl");
+
+    // --- Marching Cubes: torus isosurface ---
+    println!("\n=== Marching Cubes (torus) ===");
+    let torus = |x: f64, y: f64, z: f64| {
+        let r_major = 1.0;
+        let r_minor = 0.4;
+        let q = ((x * x + y * y).sqrt() - r_major).powi(2) + z * z;
+        q - r_minor * r_minor
+    };
+    let faces = marching_cubes(20, 20, 20, min, max, &torus, 0.0);
+    println!("  Faces: {}", faces.len());
+    let stl = faces_to_stl(&faces, "marching_cubes_torus");
+    fs::write("examples/marching_cubes_torus.stl", &stl).unwrap();
+    println!("  -> examples/marching_cubes_torus.stl");
+
+    // --- Surface to Volume (sphere) ---
+    println!("\n=== Surface to Volume (sphere) ===");
+    let tets = surface_to_volume(8, 8, 8, min, max, &sphere, 0.0);
+    println!("  Tetrahedra: {}", tets.len());
+    let stl = tetrahedra_to_stl(&tets, "surface_to_volume");
+    fs::write("examples/surface_to_volume.stl", &stl).unwrap();
+    let vtk = tetrahedra_to_vtk(&tets, "surface_to_volume");
+    fs::write("examples/surface_to_volume.vtk", &vtk).unwrap();
+    println!("  -> examples/surface_to_volume.stl, .vtk");
+
+    // --- Octree Refined ---
+    println!("\n=== Octree Refined ===");
+    let tets = octree_refined(
+        min,
+        max,
+        2,
+        &|p| p.x * p.x + p.y * p.y + p.z * p.z < 1.5 * 1.5,
+        2.0,
+    );
+    println!("  Tetrahedra: {}", tets.len());
+    let vtk = tetrahedra_to_vtk(&tets, "octree_refined");
+    fs::write("examples/octree_refined.vtk", &vtk).unwrap();
+    println!("  -> examples/octree_refined.vtk");
+
+    // --- Voxel Refined ---
+    println!("\n=== Voxel Refined ===");
+    let tets = voxel_refined(
+        min,
+        max,
+        3,
+        3,
+        3,
+        &|p| p.x * p.x + p.y * p.y + p.z * p.z < 1.5 * 1.5,
+        2.0,
+    );
+    println!("  Tetrahedra: {}", tets.len());
+    let vtk = tetrahedra_to_vtk(&tets, "voxel_refined");
+    fs::write("examples/voxel_refined.vtk", &vtk).unwrap();
+    println!("  -> examples/voxel_refined.vtk");
+
+    println!("\nDone! View STL files with MeshLab/Blender, VTK files with ParaView.");
+}

examples/simple_3d_tetrahedralization.rs

@@ -0,0 +1,64 @@
+use meshing::{bowyer_watson_3d, Point3D};
+
+fn main() {
+    let cube = vec![
+        Point3D {
+            index: 0,
+            x: 0.0,
+            y: 0.0,
+            z: 0.0,
+        },
+        Point3D {
+            index: 1,
+            x: 1.0,
+            y: 0.0,
+            z: 0.0,
+        },
+        Point3D {
+            index: 2,
+            x: 0.0,
+            y: 1.0,
+            z: 0.0,
+        },
+        Point3D {
+            index: 3,
+            x: 1.0,
+            y: 1.0,
+            z: 0.0,
+        },
+        Point3D {
+            index: 4,
+            x: 0.0,
+            y: 0.0,
+            z: 1.0,
+        },
+        Point3D {
+            index: 5,
+            x: 1.0,
+            y: 0.0,
+            z: 1.0,
+        },
+        Point3D {
+            index: 6,
+            x: 0.0,
+            y: 1.0,
+            z: 1.0,
+        },
+        Point3D {
+            index: 7,
+            x: 1.0,
+            y: 1.0,
+            z: 1.0,
+        },
+    ];
+
+    let tetrahedra = bowyer_watson_3d(cube);
+    println!("3D Delaunay tetrahedralization of a unit cube:");
+    println!("  Number of tetrahedra: {}", tetrahedra.len());
+    for (i, tet) in tetrahedra.iter().enumerate() {
+        println!(
+            "  Tet {}: ({}, {}, {}, {})",
+            i, tet.a.index, tet.b.index, tet.c.index, tet.d.index
+        );
+    }
+}

examples/sphere_mesh_export.rs

@@ -0,0 +1,66 @@
+use meshing::export::{
+    faces_to_glb, faces_to_glb_quantized, faces_to_obj, faces_to_stl, tetrahedra_to_vtk,
+};
+use meshing::marching_cubes::marching_cubes;
+use meshing::pipeline::surface_to_volume;
+use meshing::Point3D;
+use std::fs;
+
+fn main() {
+    let min = Point3D {
+        index: 0,
+        x: -2.0,
+        y: -2.0,
+        z: -2.0,
+    };
+    let max = Point3D {
+        index: 0,
+        x: 2.0,
+        y: 2.0,
+        z: 2.0,
+    };
+    let sphere = |x: f64, y: f64, z: f64| x * x + y * y + z * z - 1.0;
+
+    // Generate sphere surface mesh with marching cubes
+    println!("Generating sphere surface with marching cubes (resolution 20x20x20)...");
+    let faces = marching_cubes(20, 20, 20, min, max, &sphere, 0.0);
+    println!("  Surface faces: {}", faces.len());
+
+    // Export surface to STL
+    let stl = faces_to_stl(&faces, "sphere");
+    fs::write("examples/sphere.stl", &stl).unwrap();
+    println!("  Wrote examples/sphere.stl ({} bytes)", stl.len());
+
+    // Export surface to OBJ
+    let obj = faces_to_obj(&faces);
+    fs::write("examples/sphere.obj", &obj).unwrap();
+    println!("  Wrote examples/sphere.obj ({} bytes)", obj.len());
+
+    // Export surface to GLB
+    let glb = faces_to_glb(&faces);
+    fs::write("examples/sphere.glb", &glb).unwrap();
+    println!("  Wrote examples/sphere.glb ({} bytes)", glb.len());
+
+    // Export surface to quantized GLB
+    let glb_q = faces_to_glb_quantized(&faces);
+    fs::write("examples/sphere_quantized.glb", &glb_q).unwrap();
+    println!(
+        "  Wrote examples/sphere_quantized.glb ({} bytes, {:.0}% of regular)",
+        glb_q.len(),
+        glb_q.len() as f64 / glb.len() as f64 * 100.0
+    );
+
+    // Generate volume mesh with surface_to_volume pipeline
+    println!("\nGenerating volume mesh with surface_to_volume pipeline (8x8x8)...");
+    let tetrahedra = surface_to_volume(8, 8, 8, min, max, &sphere, 0.0);
+    println!("  Volume tetrahedra: {}", tetrahedra.len());
+
+    // Export volume to VTK
+    let vtk = tetrahedra_to_vtk(&tetrahedra, "sphere_volume");
+    fs::write("examples/sphere_volume.vtk", &vtk).unwrap();
+    println!("  Wrote examples/sphere_volume.vtk ({} bytes)", vtk.len());
+
+    println!("\nDone! Output files can be viewed with:");
+    println!("  STL/OBJ/GLB -> MeshLab, Blender, https://gltf-viewer.donmccurdy.com/");
+    println!("  VTK         -> ParaView");
+}