threedee/
├── src/
│   ├── main.js          # Main scene, camera, lighting, demo object
│   └── exporters.js     # STL/OBJ/glTF export utilities
├── user/
│   ├── models/          # User's parametric model definitions
│   └── exports/         # Generated mesh files (STL, OBJ, glTF)
└── index.html           # Viewport UI

// Basic primitives
const geometry = new THREE.BoxGeometry(2, 1, 3);           // width, height, depth
const geometry = new THREE.SphereGeometry(1, 32, 32);      // radius, segments
const geometry = new THREE.CylinderGeometry(1, 1, 2, 32);  // topR, bottomR, height
const geometry = new THREE.TorusGeometry(1, 0.4, 16, 100); // radius, tube, segments
const geometry = new THREE.TorusKnotGeometry(1, 0.35, 128, 32); // current demo

// Material
const material = new THREE.MeshStandardMaterial({
  color: 0x4a5568,    // hex color
  metalness: 0.3,     // 0-1
  roughness: 0.4,     // 0-1
});

// Create mesh and add to scene
const mesh = new THREE.Mesh(geometry, material);
mesh.position.set(x, y, z);
mesh.castShadow = true;
scene.add(mesh);

material.color.setHex(0x22d3ee);  // cyan accent

mesh.position.y = 1.5;  // lift above ground
mesh.position.set(0, 1.5, 0);  // x, y, z

mesh.scale.set(2, 1, 1);  // stretch in x

mesh.rotation.y = Math.PI / 4;  // 45 degrees

export const parameters = {
  width: 40,
  height: 20,
  depth: 40,
  color: 0x4a90d9,
};

export function createGeometry(params = parameters) {
  return new THREE.BoxGeometry(params.width, params.height, params.depth);
}

export function createMesh(params = parameters) {
  const geometry = createGeometry(params);
  const material = new THREE.MeshStandardMaterial({ color: params.color });
  return new THREE.Mesh(geometry, material);
}

// STL (3D printing)
threedeeExport.stl(mesh, "my-part")         // Binary (recommended)
threedeeExport.stlAscii(mesh, "my-part")   // ASCII text format

// General interchange
threedeeExport.obj(mesh, "my-part")        // OBJ with UVs and normals

// Web and AR
threedeeExport.gltf(mesh, "my-part")       // glTF (JSON)
threedeeExport.glb(mesh, "my-part")        // GLB (binary, compact)

// CAD interchange
threedeeExport.step(mesh, "my-part")       // STEP Faceted B-Rep

// Export to STL, OBJ, glTF, and STEP simultaneously
await threedeeExport.all(mesh, "my-part")

// Export to specific formats
await threedeeExport.all(mesh, "my-part", ['stl', 'step', 'obj'])

keyLight.intensity = 1.5;           // brighter
keyLight.position.set(10, 15, 10);  // move light
rimLight.color.setHex(0xff6600);    // orange rim