175 lines
7.7 KiB
C++
175 lines
7.7 KiB
C++
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/// \file 11_gear/main.cpp
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/// \brief Parametric gear generator — SDF → Marching Cubes → STL export
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///
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/// Demonstrates a design-exploration workflow: define gear geometry as an
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/// implicit surface (SDF), extract a triangle mesh via Marching Cubes,
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/// and export to STL for 3D printing or further processing.
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#include <vde/mesh/marching_cubes.h>
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#include <vde/mesh/halfedge_mesh.h>
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#include <vde/foundation/io_stl.h>
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#include <iostream>
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#include <iomanip>
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#include <cmath>
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#include <array>
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using namespace vde::mesh;
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using namespace vde::foundation;
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using namespace vde::core;
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// ═══════════════════════════════════════════════════════════════════════
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// Gear SDF
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// ═══════════════════════════════════════════════════════════════════════
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/**
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* @brief Build a parametric gear SDF function.
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*
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* The gear lies in the XZ plane and is extruded along the Y axis.
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* Teeth are generated as sinusoidal bumps on the pitch circle,
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* producing a simplified but visually recognizable gear profile.
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*
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* @param teeth Number of teeth
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* @param pitch_r Pitch circle radius
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* @param addendum Tooth height above pitch circle
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* @param dedendum Tooth depth below pitch circle
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* @param thickness Total thickness (Y-axis extrusion)
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* @return SDF function f(x, y, z) → signed distance
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*/
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inline auto make_gear_sdf(int teeth, double pitch_r,
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double addendum, double dedendum,
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double thickness) {
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return [=](double x, double y, double z) -> double {
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// ── 2D gear profile in XZ plane ──
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double r = std::sqrt(x * x + z * z);
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double theta = std::atan2(z, x);
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// Root circle (inner)
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double root_r = pitch_r - dedendum;
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double d_root = r - root_r;
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// Tooth profile: sinusoidal bumps
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// cos(N*theta) = +1 at tooth center, -1 at gap center
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// radius at tooth center = pitch_r + addendum
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// radius at gap center = pitch_r - dedendum
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double bump = (addendum + dedendum) * 0.5 * (1.0 + std::cos(teeth * theta));
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double prof_r = root_r + bump;
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double d_tooth = r - prof_r;
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// Union: point is inside if inside root circle OR inside tooth profile
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double d_xy = std::min(d_root, d_tooth);
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// ── Extrude along Y axis ──
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double d_y = std::abs(y) - thickness * 0.5;
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return std::max(d_xy, d_y);
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};
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}
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// ═══════════════════════════════════════════════════════════════════════
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// Main — Parametric Gear
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// ═══════════════════════════════════════════════════════════════════════
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int main() {
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std::cout << std::fixed << std::setprecision(2);
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std::cout << "╔══════════════════════════════════╗\n"
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<< "║ Gear — Parametric SDF Demo ║\n"
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<< "╚══════════════════════════════════╝\n\n";
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// ── Parameters ───────────────────────────────────────────────────
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//
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// Standard involute gear parameters (simplified):
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// module = pitch diameter / teeth → standard metric sizing
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// tooth height = 2.25 × module (addendum + dedendum)
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const int teeth = 16;
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const double module = 2.0;
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const double pitch_r = teeth * module / 2.0; // 16 mm
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const double addendum = module; // 2 mm
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const double dedendum = 1.25 * module; // 2.5 mm
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const double thickness = 10.0;
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std::cout << "Parameters:\n"
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<< " teeth: " << teeth << "\n"
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<< " module: " << module << " mm\n"
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<< " pitch Ø: " << pitch_r * 2.0 << " mm\n"
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<< " outer Ø: " << (pitch_r + addendum) * 2.0 << " mm\n"
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<< " root Ø: " << (pitch_r - dedendum) * 2.0 << " mm\n"
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<< " thickness: " << thickness << " mm\n\n";
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// ── Step 1: Marching Cubes — SDF → triangle mesh ─────────────────
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//
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// Sample a bounding box slightly larger than the gear,
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// at 128³ voxel resolution for smooth teeth.
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const double bb_margin = addendum + dedendum + 2.0;
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const double bb_r = pitch_r + addendum + bb_margin;
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const int res = 128;
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std::cout << "Step 1: Marching Cubes (resolution " << res << "³)\n";
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auto gear_sdf = make_gear_sdf(teeth, pitch_r, addendum, dedendum, thickness);
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MCMesh mc = marching_cubes(gear_sdf, 0.0,
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Point3D(-bb_r, -thickness - 2, -bb_r),
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Point3D( bb_r, thickness + 2, bb_r),
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res);
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std::cout << " vertices: " << mc.vertices.size() << "\n"
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<< " triangles: " << mc.triangles.size() << "\n";
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// ── Step 2: Build half-edge mesh ─────────────────────────────────
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std::cout << "\nStep 2: Build HalfedgeMesh\n";
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HalfedgeMesh mesh;
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mesh.build_from_triangles(mc.vertices, mc.triangles);
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mesh.update_normals();
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std::cout << " vertices: " << mesh.num_vertices() << "\n"
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<< " faces: " << mesh.num_faces() << "\n"
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<< " edges: " << mesh.num_edges() << "\n";
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// ── Step 3: Export to STL ────────────────────────────────────────
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std::cout << "\nStep 3: Export STL (binary)\n";
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std::vector<StlTriangle> stl_tris;
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stl_tris.reserve(mesh.num_faces());
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for (size_t fi = 0; fi < mesh.num_faces(); ++fi) {
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auto verts = mesh.face_vertices(static_cast<int>(fi));
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if (verts.size() < 3) continue;
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const Point3D& a = mesh.vertex(static_cast<size_t>(verts[0]));
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const Point3D& b = mesh.vertex(static_cast<size_t>(verts[1]));
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const Point3D& c = mesh.vertex(static_cast<size_t>(verts[2]));
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Vector3D n = (b - a).cross(c - a).normalized();
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StlTriangle t;
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t.normal = n;
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t.v0 = a;
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t.v1 = b;
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t.v2 = c;
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stl_tris.push_back(t);
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}
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const char* stl_path = "gear.stl";
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write_stl(stl_path, stl_tris);
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std::cout << " → " << stl_path << " (" << stl_tris.size()
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<< " triangles)\n";
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// ── Summary ──────────────────────────────────────────────────────
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std::cout << "\n╔══════════════════════════════════════════╗\n"
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<< "║ Gear Export Summary ║\n"
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<< "╠══════════════════════════════════════════╣\n"
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<< "║ SDF → Marching Cubes → STL ✓ ║\n"
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<< "╚══════════════════════════════════════════╝\n";
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std::cout << "\nDone! Parametric gear exported.\n";
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return 0;
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}
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