使用 Three.js 实现【程序化草地效果】，具体要求：

【核心特效】
- 程序化草叶生成
- 风吹动画效果
- 云影投影
- 颜色渐变

【场景与光照】
- 天空盒背景
- 自发光草叶

【交互与控制】
- OrbitControls 轨道控制器

【技术要求】
- Three.js 最新版本
- 自定义 BufferGeometry
- ShaderMaterial 自定义着色器
- 纹理驱动的云影

class GrassGeometry extends THREE.BufferGeometry {
  constructor(size, count) {
    super();
    const positions = [];
    const uvs = [];
    const indices = [];

    for (let i = 0; i < count; i++) {
      const radius = (size / 2) * Math.random();
      const theta = Math.random() * 2 * Math.PI;
      const x = radius * Math.cos(theta);
      const y = radius * Math.sin(theta);

      const blade = this.computeBlade([x, 0, y], i);
      positions.push(...blade.positions);
      indices.push(...blade.indices);
    }

    this.setAttribute('position', new THREE.BufferAttribute(new Float32Array(positions), 3));
    this.setIndex(indices);
  }
}

float wave(float waveSize, float tipDistance, float centerDistance) {
  bool isTip = (gl_VertexID + 1) % 5 == 0;
  float waveDistance = isTip ? tipDistance : centerDistance;
  return sin((uTime / 500.0) + waveSize) * waveDistance;
}

void main() {
  vPosition = position;

  // 云影移动
  vUv.x += uTime * 0.0001 * offsetX;
  vUv.y += uTime * 0.0001 * offsetY;

  if (vPosition.y < 0.0) {
    vPosition.y = 0.0;
  } else {
    vPosition.x += wave(uv.x * 10.0, 0.3, 0.1);
  }

  gl_Position = projectionMatrix * modelViewMatrix * vec4(vPosition, 1.0);
}

vec3 green = vec3(0.2, 0.6, 0.3);
vec3 color = mix(green * 0.7, green, vPosition.y);
color = mix(color, texture2D(uCloud, vUv).rgb, 0.4);
float lighting = normalize(dot(vNormal, vec3(10)));
gl_FragColor = vec4(color + lighting * 0.03, 1.0);