const lod = new THREE.LOD();
const lowDetailModel = ... // 低細(xì)節(jié)模型
const midDetailModel = ... // 中細(xì)節(jié)模型
const highDetailModel = ... // 高細(xì)節(jié)模型
lod.addLevel(lowDetailModel, 0); // 添加低細(xì)節(jié)模型，距離為0
lod.addLevel(midDetailModel, 100); // 添加中細(xì)節(jié)模型，距離為100
lod.addLevel(highDetailModel, 200); // 添加高細(xì)節(jié)模型，距離為200

scene.add(lod);

function render() {
  requestAnimationFrame(render);
  lod.update(camera);
  renderer.render(scene, camera);
}

const texture = new THREE.TextureLoader().load('atlas.png');
const material = new THREE.MeshBasicMaterial({ map: texture });

const geometry = new THREE.BoxGeometry(1, 1, 1);
const uvAttribute = geometry.attributes.uv;
for (let i = 0; i < uvAttribute.count; i++) {
  const u = uvAttribute.getX(i);
  const v = uvAttribute.getY(i);
  // 根據(jù)小紋理圖在大紋理圖中的位置和大小計(jì)算出UV坐標(biāo)
  uvAttribute.setXY(i, u * smallTextureWidth / bigTextureWidth + smallTextureX / bigTextureWidth, v * smallTextureHeight / bigTextureHeight + smallTextureY / bigTextureHeight);
}

function render() {
  requestAnimationFrame(render);
  const time = Date.now() * 0.001;
  texture.offset.x = time * 0.1; // x方向偏移量
  texture.offset.y = time * 0.2; // y方向偏移量
  texture.repeat.set(2, 2); // 橫向和縱向縮放值
  renderer.render(scene, camera);
}

const geometry = new THREE.BoxGeometry(1, 1, 1);
const material = new THREE.MeshBasicMaterial({ color: 0xff0000 });

const instances = 10000; // 實(shí)例數(shù)量
const instancedGeometry = new THREE.InstancedBufferGeometry();
instancedGeometry.copy(geometry); // 復(fù)制幾何體屬性
const translations = new Float32Array(instances * 3); // 實(shí)例位置數(shù)組
for (let i = 0; i < instances; i++) {
  translations[i * 3] = Math.random() * 100 - 50;
  translations[i * 3 + 1] = Math.random() * 100 - 50;
  translations[i * 3 + 2] = Math.random() * 100 - 50;
}
instancedGeometry.setAttribute('translation', new THREE.InstancedBufferAttribute(translations, 3));

const instancedMesh = new THREE.InstancedMesh(instancedGeometry, material, instances);
scene.add(instancedMesh);

function render() {
  requestAnimationFrame(render);
  const time = Date.now() * 0.001;
  for (let i = 0; i < instances; i++) {
    const translation = instancedMesh.geometry.attributes.translation;
    translation.setXYZ(i, Math.sin(time + i * 0.5) * 5, Math.cos(time + i * 0.3) * 5, i * 0.1);
  }
  instancedMesh.geometry.attributes.translation.needsUpdate = true; // 更新實(shí)例位置屬性
  renderer.render(scene, camera);
}

const renderer = new THREE.WebGLRenderer({ canvas: canvas, context: canvas.getContext('webgl2') });

const transformFeedback = new THREE.WebGL2TransformFeedback();
const bufferGeometry = new THREE.BufferGeometry();
const positions = new Float32Array([0, 0, 0]);
bufferGeometry.setAttribute('position', new THREE.BufferAttribute(positions, 3));
const shader = new THREE.ShaderMaterial({
  vertexShader: `
    out vec3 transformedPosition;
    void main() {
      transformedPosition = position;
      gl_Position = projectionMatrix * modelViewMatrix * vec4(position, 1.0);
    }
  `,
  fragmentShader: `
    void main() {
      gl_FragColor = vec4(1.0);
    }
  `,
  transformFeedback: {
    // 將頂點(diǎn)位置記錄到transformedPosition變量中
    varyings: ['transformedPosition'],
    // 開(kāi)啟transform feedback
    enabled: true,
    // 設(shè)置bufferGeometry的位置屬性為transform feedback的輸出屬性
    bufferGeometry: bufferGeometry
  }
});
const mesh = new THREE.Mesh(bufferGeometry, shader);
scene.add(mesh);
function render() {
  requestAnimationFrame(render);
  renderer.setRenderTarget(null);
  // 開(kāi)始transform feedback
  transformFeedback.begin();
  renderer.render(scene, camera);
  // 結(jié)束transform feedback，并將變化后的頂點(diǎn)位置存儲(chǔ)到bufferGeometry中
  transformFeedback.end();
  // 更新頂點(diǎn)位置
  positions.set(bufferGeometry.getAttribute('position').array);
  bufferGeometry.setAttribute('position', new THREE.BufferAttribute(positions, 3));
  renderer.render(scene, camera);
}

const worker = new Worker('worker.js');

// worker.js
function process(data) {
  // 計(jì)算密集型的任務(wù)
  return result;
}
onmessage = function(event) {
  const result = process(event.data);
  postMessage(result);
};

function render() {
  requestAnimationFrame(render);
  // 發(fā)送任務(wù)到Web Worker
  worker.postMessage(data);
  worker.onmessage = function(event) {
    const result = event.data;
    // 處理返回結(jié)果
  };
  renderer.render(scene, camera);
}

function render() {
  // 渲染代碼
  renderer.render(scene, camera);
  // 請(qǐng)求下一幀動(dòng)畫(huà)
  requestAnimationFrame(render);
}

var animationId = requestAnimationFrame(render);

function stop() {
  cancelAnimationFrame(animationId);
}