# Three.js Geometry

## Quick Start

```javascript
import * as THREE from "three";

// Built-in geometry
const box = new THREE.BoxGeometry(1, 1, 1);
const sphere = new THREE.SphereGeometry(0.5, 32, 32);
const plane = new THREE.PlaneGeometry(10, 10);

// Create mesh
const material = new THREE.MeshStandardMaterial({ color: 0x00ff00 });
const mesh = new THREE.Mesh(box, material);
scene.add(mesh);
```

## Built-in Geometries

### Basic Shapes

```javascript
// Box - width, height, depth, widthSegments, heightSegments, depthSegments
new THREE.BoxGeometry(1, 1, 1, 1, 1, 1);

// Sphere - radius, widthSegments, heightSegments, phiStart, phiLength, thetaStart, thetaLength
new THREE.SphereGeometry(1, 32, 32);
new THREE.SphereGeometry(1, 32, 32, 0, Math.PI * 2, 0, Math.PI); // Full sphere
new THREE.SphereGeometry(1, 32, 32, 0, Math.PI); // Hemisphere

// Plane - width, height, widthSegments, heightSegments
new THREE.PlaneGeometry(10, 10, 1, 1);

// Circle - radius, segments, thetaStart, thetaLength
new THREE.CircleGeometry(1, 32);
new THREE.CircleGeometry(1, 32, 0, Math.PI); // Semicircle

// Cylinder - radiusTop, radiusBottom, height, radialSegments, heightSegments, openEnded
new THREE.CylinderGeometry(1, 1, 2, 32, 1, false);
new THREE.CylinderGeometry(0, 1, 2, 32); // Cone
new THREE.CylinderGeometry(1, 1, 2, 6); // Hexagonal prism

// Cone - radius, height, radialSegments, heightSegments, openEnded
new THREE.ConeGeometry(1, 2, 32, 1, false);

// Torus - radius, tube, radialSegments, tubularSegments, arc
new THREE.TorusGeometry(1, 0.4, 16, 100);

// TorusKnot - radius, tube, tubularSegments, radialSegments, p, q
new THREE.TorusKnotGeometry(1, 0.4, 100, 16, 2, 3);

// Ring - innerRadius, outerRadius, thetaSegments, phiSegments
new THREE.RingGeometry(0.5, 1, 32, 1);
```

### Advanced Shapes

```javascript
// Capsule - radius, length, capSegments, radialSegments
new THREE.CapsuleGeometry(0.5, 1, 4, 8);

// Dodecahedron - radius, detail
new THREE.DodecahedronGeometry(1, 0);

// Icosahedron - radius, detail (0 = 20 faces, higher = smoother)
new THREE.IcosahedronGeometry(1, 0);

// Octahedron - radius, detail
new THREE.OctahedronGeometry(1, 0);

// Tetrahedron - radius, detail
new THREE.TetrahedronGeometry(1, 0);

// Polyhedron - vertices, indices, radius, detail
const vertices = [1, 1, 1, -1, -1, 1, -1, 1, -1, 1, -1, -1];
const indices = [2, 1, 0, 0, 3, 2, 1, 3, 0, 2, 3, 1];
new THREE.PolyhedronGeometry(vertices, indices, 1, 0);
```

### Path-Based Shapes

```javascript
// Lathe - points[], segments, phiStart, phiLength
const points = [
  new THREE.Vector2(0, 0),
  new THREE.Vector2(0.5, 0),
  new THREE.Vector2(0.5, 1),
  new THREE.Vector2(0, 1),
];
new THREE.LatheGeometry(points, 32);

// Extrude - shape, options
const shape = new THREE.Shape();
shape.moveTo(0, 0);
shape.lineTo(1, 0);
shape.lineTo(1, 1);
shape.lineTo(0, 1);
shape.lineTo(0, 0);

const extrudeSettings = {
  steps: 2,
  depth: 1,
  bevelEnabled: true,
  bevelThickness: 0.1,
  bevelSize: 0.1,
  bevelSegments: 3,
};
new THREE.ExtrudeGeometry(shape, extrudeSettings);

// Tube - path, tubularSegments, radius, radialSegments, closed
const curve = new THREE.CatmullRomCurve3([
  new THREE.Vector3(-1, 0, 0),
  new THREE.Vector3(0, 1, 0),
  new THREE.Vector3(1, 0, 0),
]);
new THREE.TubeGeometry(curve, 64, 0.2, 8, false);
```

### Text Geometry

```javascript
import { FontLoader } from "three/examples/jsm/loaders/FontLoader.js";
import { TextGeometry } from "three/examples/jsm/geometries/TextGeometry.js";

const loader = new FontLoader();
loader.load("fonts/helvetiker_regular.typeface.json", (font) => {
  const geometry = new TextGeometry("Hello", {
    font: font,
    size: 1,
    depth: 0.2, // Was 'height' in older versions
    curveSegments: 12,
    bevelEnabled: true,
    bevelThickness: 0.03,
    bevelSize: 0.02,
    bevelSegments: 5,
  });

  // Center text
  geometry.computeBoundingBox();
  geometry.center();

  const mesh = new THREE.Mesh(geometry, material);
  scene.add(mesh);
});
```

## BufferGeometry

The base class for all geometries. Stores data as typed arrays for GPU efficiency.

### Custom BufferGeometry

```javascript
const geometry = new THREE.BufferGeometry();

// Vertices (3 floats per vertex: x, y, z)
const vertices = new Float32Array([
  -1,
  -1,
  0, // vertex 0
  1,
  -1,
  0, // vertex 1
  1,
  1,
  0, // vertex 2
  -1,
  1,
  0, // vertex 3
]);
geometry.setAttribute("position", new THREE.BufferAttribute(vertices, 3));

// Indices (for indexed geometry - reuse vertices)
const indices = new Uint16Array([
  0,
  1,
  2, // triangle 1
  0,
  2,
  3, // triangle 2
]);
geometry.setIndex(new THREE.BufferAttribute(indices, 1));

// Normals (required for lighting)
const normals = new Float32Array([0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1]);
geometry.setAttribute("normal", new THREE.BufferAttribute(normals, 3));

// UVs (for texturing)
const uvs = new Float32Array([0, 0, 1, 0, 1, 1, 0, 1]);
geometry.setAttribute("uv", new THREE.BufferAttribute(uvs, 2));


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