实现下雪的效果，就需要一个雪花纹理或者通过canvas绘制的雪花，这里通过给每个粒子设置纹理贴图来实现雪花粒子。
示例：http://ithanmang.com/threeJs/home/201808/20180815/02-snow-scene.html
效果
1、首先，需要加载纹理。
/* 雪花图片 */
let texture = new THREE.TextureLoader().load('../../textures/particles/snowflake2.png');
2、样式化材质，加入贴图
let pointsMaterial = new THREE.PointsMaterial({
size:5,
transparent:true,
opacity:0.9,
map:texture,
blending:THREE.AdditiveBlending,
sizeAttenuation:true,
depthTest: false
});3、创建几何体并设置每一个顶点
let geometry= new THREE.Geometry();
let range = 100;
for (let i = 0; i < 1500; i++ ) {
let vertice = new THREE.Vector3(
Math.random() * range - range / 2,
Math.random() * range * 1.5,
Math.random() * range - range / 2);
/* 纵向移动速度 */
vertice.velocityY = 0.1 + Math.random() / 5;
/* 横向移动速度 */
vertice.velocityX = (Math.random() - 0.5) / 3;
/* 将顶点加入几何 */
geometry.vertices.push(vertice);
}
geometry.center();
points = new THREE.Points(geometry, pointsMaterial);
scene.add(points);
4、更新粒子的顶点数据
/* 数据更新 */
function update() {
stats.update();
let vertices = points.geometry.vertices;
vertices.forEach(function (v) {
v.y = v.y - (v.velocityY);
v.x = v.x - (v.velocityX);
if (v.y <= 0) v.y = 60;
if (v.x <= -20 || v.x >= 20) v.velocityX = v.velocityX * -1;
});
/* 顶点变动之后需要更新，否则无法实现雨滴特效 */
points.geometry.verticesNeedUpdate = true;
}需要注意的是，
Geometry的vertices数据变化后，需要更新，否则不会自动刷新，同样包括color、linedistances等属性变动之后都需要更新。
示例代码
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Sprite 粒子（精灵）示例</title>
<style>
body {
margin: 0;
overflow: hidden;/* 溢出隐藏 */
}
</style>
<script src="../../libs/build/three-r93.js"></script>
<script src="../../libs/examples/js/Detector.js"></script>
<script src="../../libs/examples/js/libs/dat.gui.min.js"></script>
<script src="../../libs/examples/js/libs/stats.min.js"></script>
<script src="../../libs/examples/js/controls/OrbitControls.js"></script>
</head>
<body>
<script>
let scene, camera, renderer, controls, points;
let stats = initStats();
/* 场景 */
function initScene() {
scene = new THREE.Scene();
}
/* 相机 */
function initCamera() {
camera = new THREE.PerspectiveCamera(45, window.innerWidth / window.innerHeight, 0.1, 10000);
camera.position.set(30, 0, 80);
camera.lookAt(new THREE.Vector3(0, 0, 0));
}
/* 渲染器 */
function initRender() {
renderer = new THREE.WebGLRenderer({antialias: true});
renderer.setSize(window.innerWidth, window.innerHeight);
document.body.appendChild(renderer.domElement);
}
/* 灯光 */
function initLight() {
}
/* 控制器 */
function initControls() {
controls = new THREE.OrbitControls(camera, renderer.domElement);
/* 属性参数默认 */
}
/* 场景中的内容 */
function initContent() {
/* 雪花图片 */
let texture = new THREE.TextureLoader().load('../../textures/particles/snowflake2.png');
let geometry= new THREE.Geometry();
let pointsMaterial = new THREE.PointsMaterial({
size:2,
transparent:true,
opacity:0.8,
map:texture,
blending:THREE.AdditiveBlending,
sizeAttenuation:true,
depthTest: false
});
let range = 100;
for (let i = 0; i < 1500; i++ ) {
let vertice = new THREE.Vector3(
Math.random() * range - range / 2,
Math.random() * range * 1.5,
Math.random() * range - range / 2);
/* 纵向移动速度 */
vertice.velocityY = 0.1 + Math.random() / 3;
/* 横向移动速度 */
vertice.velocityX = (Math.random() - 0.5) / 3;
/* 将顶点加入几何 */
geometry.vertices.push(vertice);
}
geometry.center();
points = new THREE.Points(geometry, pointsMaterial);
points.position.y = -30;
scene.add(points);
}
/* 性能插件 */
function initStats() {
let stats = new Stats();
document.body.appendChild(stats.domElement);
return stats;
}
/* 窗口变动触发 */
function onWindowResize() {
camera.aspect = window.innerWidth / window.innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(window.innerWidth, window.innerHeight);
}
/* 数据更新 */
function update() {
stats.update();
let vertices = points.geometry.vertices;
vertices.forEach(function (v) {
v.y = v.y - (v.velocityY);
v.x = v.x - (v.velocityX);
if (v.y <= 0) v.y = 60;
if (v.x <= -20 || v.x >= 20) v.velocityX = v.velocityX * -1;
});
/* 顶点变动之后需要更新，否则无法实现雨滴特效 */
points.geometry.verticesNeedUpdate = true;
}
/* 初始化 */
function init() {
initScene();
initCamera();
initRender();
initLight();
initControls();
initContent();
/* 监听事件 */
window.addEventListener('resize', onWindowResize, false);
}
/* 循环渲染 */
function animate() {
requestAnimationFrame(animate);
renderer.render(scene, camera);
update();
}
/* 初始加载 */
(function () {
console.log("three init start...");
init();
animate();
console.log("three init send...");
})();
</script>
</body>
</html>