 makeSpriteTexture(textureSize, obj) {
  const rt = new THREE.WebGLRenderTarget(textureSize, textureSize);

  const aspect = 1;  // 因为Render Target是正方形
  const camera = new THREE.PerspectiveCamera(fov, aspect, near, far);

  scene.add(obj);

  // 计算对象的盒模型
  const box = new THREE.Box3().setFromObject(obj);

  const boxSize = box.getSize(new THREE.Vector3());
  const boxCenter = box.getCenter(new THREE.Vector3());

  // 设置相机去构建盒模型
  const fudge = 1.1;
  const si