ViewDesignEngine/examples/08_3d_print/main.cpp

/// \file   08_3d_print/main.cpp
/// \brief  Complete 3D printing pipeline: SDF → marching cubes → mesh stats → STL export
///
/// Demonstrates end-to-end workflow from parametric SDF shape definition to
/// a slicer-ready STL file, with mesh quality statistics along the way.

#include <vde/sdf/sdf_primitives.h>
#include <vde/sdf/sdf_operations.h>
#include <vde/sdf/sdf_to_mesh.h>
#include <vde/mesh/marching_cubes.h>
#include <vde/mesh/halfedge_mesh.h>
#include <vde/foundation/io_stl.h>
#include <vde/core/aabb.h>

#include <iostream>
#include <iomanip>
#include <cmath>

using namespace vde::core;
using namespace vde::sdf;
using namespace vde::mesh;
using namespace vde::foundation;

// ── helpers ──

/// Compute approximate volume via divergence theorem (loop over faces)
static double compute_volume(const HalfedgeMesh& m) {
    double vol = 0.0;
    for (size_t fi = 0; fi < m.num_faces(); ++fi) {
        auto verts = m.face_vertices(fi);
        if (verts.size() < 3) continue;
        const Point3D& a = m.vertex(verts[0]);
        const Point3D& b = m.vertex(verts[1]);
        const Point3D& c = m.vertex(verts[2]);
        // Signed volume contribution: (1/6) * (a · (b × c))
        vol += a.x() * (b.y() * c.z() - b.z() * c.y())
             + a.y() * (b.z() * c.x() - b.x() * c.z())
             + a.z() * (b.x() * c.y() - b.y() * c.x());
    }
    return std::abs(vol) / 6.0;
}

/// Convert HalfedgeMesh faces to STL triangles
static std::vector<StlTriangle> to_stl_triangles(const HalfedgeMesh& m) {
    std::vector<StlTriangle> tris;
    tris.reserve(m.num_faces());

    for (size_t fi = 0; fi < m.num_faces(); ++fi) {
        auto verts = m.face_vertices(fi);
        if (verts.size() < 3) continue;
        StlTriangle t;
        t.normal = m.face_normal(static_cast<int>(fi));
        t.v0 = m.vertex(verts[0]);
        t.v1 = m.vertex(verts[1]);
        t.v2 = m.vertex(verts[2]);
        tris.push_back(t);
    }
    return tris;
}

// ═══════════════════════════════════════════════════════════════════════
//  Main — 3D Print Pipeline
// ═══════════════════════════════════════════════════════════════════════

int main() {
    std::cout << std::fixed << std::setprecision(4);
    std::cout << "╔══════════════════════════════════╗\n"
              << "║   3D Print Pipeline             ║\n"
              << "╚══════════════════════════════════╝\n\n";

    // ── Step 1: Define the SDF shape ─────────────────────────────────
    //
    // A smooth blend between a box and a torus creates an organic-looking
    // shape that would be challenging to model with traditional CAD.

    std::cout << "Step 1: Define SDF shape\n";

    // Use Point3D overloads from sdf_primitives.h for type safety
    auto shape_sdf = [](double x, double y, double z) -> double {
        Point3D p(x, y, z);
        double d_box   = box(p, Point3D(2.0, 2.0, 2.0));
        double d_torus = torus(p, 1.5, 0.3);
        return op_smooth_union(d_box, d_torus, 0.4);
    };

    std::cout << "  shape = op_smooth_union( box(2,2,2), torus(1.5, 0.3), k=0.4 )\n";

    // ── Step 2: Marching cubes → triangle mesh ───────────────────────

    std::cout << "\nStep 2: Extract isosurface via marching cubes\n";

    const Point3D bmin(-3.0, -3.0, -3.0);
    const Point3D bmax( 3.0,  3.0,  3.0);
    const int    resolution = 80;

    auto mc = marching_cubes(shape_sdf, 0.0, bmin, bmax, resolution);

    std::cout << "  grid: " << resolution << "³  (" << resolution
              << " samples per axis)\n";
    std::cout << "  raw triangles: " << mc.triangles.size() << "\n";

    // ── Step 3: Build half-edge mesh & print stats ───────────────────

    std::cout << "\nStep 3: Build half-edge mesh + stats\n";

    HalfedgeMesh mesh;
    mesh.build_from_triangles(mc.vertices, mc.triangles);
    mesh.update_normals();

    AABB3D bb = mesh.bounds();

    std::cout << "  vertices:   " << mesh.num_vertices() << "\n"
              << "  faces:      " << mesh.num_faces() << "\n"
              << "  edges:      " << mesh.num_edges() << "\n"
              << "  volume:     " << compute_volume(mesh) << " (approx)\n"
              << "  bounding box:\n"
              << "    min:  (" << bb.min().x() << ", " << bb.min().y() << ", " << bb.min().z() << ")\n"
              << "    max:  (" << bb.max().x() << ", " << bb.max().y() << ", " << bb.max().z() << ")\n"
              << "    size: (" << bb.max().x() - bb.min().x() << ", "
                                   << bb.max().y() - bb.min().y() << ", "
                                   << bb.max().z() - bb.min().z() << ")\n";

    // ── Step 4: Export STL (binary, for slicers) ─────────────────────

    std::cout << "\nStep 4: Export STL for slicing\n";

    const char* out_path = "output_3d_print.stl";
    auto stl_tris = to_stl_triangles(mesh);
    write_stl(out_path, stl_tris);

    std::cout << "  → " << out_path << "  (" << stl_tris.size()
              << " triangles, binary format)\n";
    std::cout << "  Slicer-ready! Open in PrusaSlicer, Cura, or Bambu Studio.\n";

    // ── Bonus: ASCII variant for inspection ──────────────────────────

    const char* ascii_path = "output_3d_print_ascii.stl";
    write_stl_ascii(ascii_path, stl_tris);
    std::cout << "  → " << ascii_path << "  (ASCII, human-readable)\n";

    std::cout << "\nDone.\n";
    return 0;
}