随机粒子效果 · Random · ▶ 在线运行案例
案例合集： 三维可视化功能案例（threehub.cn）
开源仓库github地址： https://github.com/z2586300277/three-cesium-examples
**400个案例代码: ** 网盘链接
你将学到什么
- onBeforeCompile 注入 GLSL 改造内置材质
- OrbitControls 相机轨道交互
- BufferGeometry 自定义顶点/索引数据
- 监听窗口
resize同步更新 camera 与 renderer
效果说明
本案例演示 随机粒子效果 效果：基于 WebGL 实现「随机粒子效果」可视化效果，附完整可运行源码；核心用到 onBeforeCompile、OrbitControls、BufferGeometry。建议先打开文首在线案例查看动态画面，再对照下方源码逐步理解。
核心概念
- Scene / Camera / WebGLRenderer 构成最小渲染闭环；大场景可开
logarithmicDepthBuffer缓解 Z-fighting。 - onBeforeCompile 在 Three 拼好内置 shader 后替换
#include <xxx>片段，适合在 PBR 材质上叠加大屏特效。 - OrbitControls 提供轨道旋转/缩放；开启
enableDamping后需在 animate 中controls.update()。
实现步骤
- 搭建灯光与环境（如有）
- requestAnimationFrame 循环 update + render
代码要点
<!DOCTYPE html>
<html lang="en">
<head>
<title>three.js</title>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, user-scalable=no, minimum-scale=1.0, maximum-scale=1.0">
</head>
<body>
<script type="importmap">
{
"imports": {
"three": "https://threejs.org/build/three.module.js",
"three/addons/": "https://threejs.org/examples/jsm/"
}
}
</script>
<script>
let noise = `// Simplex 4D Noise
// by Ian McEwan, Ashima Arts
//
vec4 permute(vec4 x){return mod(((x*34.0)+1.0)*x, 289.0);}
float permute(float x){return floor(mod(((x*34.0)+1.0)*x, 289.0));}
vec4 taylorInvSqrt(vec4 r){return 1.79284291400159 - 0.85373472095314 * r;}
float taylorInvSqrt(float r){return 1.79284291400159 - 0.85373472095314 * r;}
vec4 grad4(float j, vec4 ip){
const vec4 ones = vec4(1.0, 1.0, 1.0, -1.0);
vec4 p,s;
p.xyz = floor( fract (vec3(j) * ip.xyz) * 7.0) * ip.z - 1.0;
p.w = 1.5 - dot(abs(p.xyz), ones.xyz);
s = vec4(lessThan(p, vec4(0.0)));
p.xyz = p.xyz + (s.xyz*2.0 - 1.0) * s.www;
return p;
}
float snoise(vec4 v){
const vec2 C = vec2( 0.138196601125010504, // (5 - sqrt(5))/20 G4
0.309016994374947451); // (sqrt(5) - 1)/4 F4
// First corner
vec4 i = floor(v + dot(v, C.yyyy) );
vec4 x0 = v - i + dot(i, C.xxxx);
// Other corners
// Rank sorting originally contributed by Bill Licea-Kane, AMD (formerly ATI)
vec4 i0;
vec3 isX = step( x0.yzw, x0.xxx );
vec3 isYZ = step( x0.zww, x0.yyz );
// i0.x = dot( isX, vec3( 1.0 ) );
i0.x = isX.x + isX.y + isX.z;
i0.yzw = 1.0 - isX;
// i0.y += dot( isYZ.xy, vec2( 1.0 ) );
i0.y += isYZ.x + isYZ.y;
i0.zw += 1.0 - isYZ.xy;
i0.z += isYZ.z;
i0.w += 1.0 - isYZ.z;
// i0 now contains the unique values 0,1,2,3 in each channel
vec4 i3 = clamp( i0, 0.0, 1.0 );
vec4 i2 = clamp( i0-1.0, 0.0, 1.0 );
vec4 i1 = clamp( i0-2.0, 0.0, 1.0 );
// x0 = x0 - 0.0 + 0.0 * C
vec4 x1 = x0 - i1 + 1.0 * C.xxxx;
vec4 x2 = x0 - i2 + 2.0 * C.xxxx;
vec4 x3 = x0 - i3 + 3.0 * C.xxxx;
vec4 x4 = x0 - 1.0 + 4.0 * C.xxxx;
// Permutations
i = mod(i, 289.0);
float j0 = permute( permute( permute( permute(i.w) + i.z) + i.y) + i.x);
vec4 j1 = permute( permute( permute( permute (
i.w + vec4(i1.w, i2.w, i3.w, 1.0 ))
+ i.z + vec4(i1.z, i2.z, i3.z, 1.0 ))
+ i.y + vec4(i1.y, i2.y, i3.y, 1.0 ))
+ i.x + vec4(i1.x, i2.x, i3.x, 1.0 ));
// Gradients
// ( 7*7*6 points uniformly over a cube, mapped onto a 4-octahedron.)
// 7*7*6 = 294, which is close to the ring size 17*17 = 289.
vec4 ip = vec4(1.0/294.0, 1.0/49.0, 1.0/7.0, 0.0) ;
vec4 p0 = grad4(j0, ip);
vec4 p1 = grad4(j1.x, ip);
vec4 p2 = grad4(j1.y, ip);
vec4 p3 = grad4(j1.z, ip);
vec4 p4 = grad4(j1.w, ip);
// Normalise gradients
vec4 norm = taylorInvSqrt(vec4(dot(p0,p0), dot(p1,p1), dot(p2, p2), dot(p3,p3)));
p0 *= norm.x;
p1 *= norm.y;
p2 *= norm.z;
p3 *= norm.w;
p4 *= taylorInvSqrt(dot(p4,p4));
// Mix contributions from the five corners
vec3 m0 = max(0.6 - vec3(dot(x0,x0), dot(x1,x1), dot(x2,x2)), 0.0);
vec2 m1 = max(0.6 - vec2(dot(x3,x3), dot(x4,x4) ), 0.0);
m0 = m0 * m0;
m1 = m1 * m1;
return 49.0 * ( dot(m0*m0, vec3( dot( p0, x0 ), dot( p1, x1 ), dot( p2, x2 )))
+ dot(m1*m1, vec2( dot( p3, x3 ), dot( p4, x4 ) ) ) ) ;
}`;
</script>
<script type="module">
import * as THREE from "three";
import { OrbitControls } from "three/addons/controls/OrbitControls.js";
class Particles extends THREE.Points {
constructor(gu) {
let particlePos = []; //vec4 (speed, shift radius, phase, reserved);
let particleAlpha = []; //vec4 (phase, speed, reserved, reserved)
let g = new THREE.BufferGeometry()
.setFromPoints(
new Array(1000).fill().map((_) => {
particlePos.push(
Math.random() * 0.2 + 0.2,
Math.random() + 1,
Math.random(),
0
);
particleAlpha.push(
Math.random(),
Math.random() * 0.4 + 0.1,
0,
0
);
let r = 5;
return new THREE.Vector3().setFromCylindricalCoords(
Math.sqrt(r * r * Math.random()),
Math.random() * Math.PI * 2,
Math.random() * 10
);
})
)
.setAttribute(
"particlePos",
new THREE.Float32BufferAttribute(particlePos, 4)
)
.setAttribute(
"particleAlpha",
new THREE.Float32BufferAttribute(particleAlpha, 4)
);
let m = new THREE.PointsMaterial({
size: 0.5,
color: "white",
transparent: true,
depthTest: false,
onBeforeCompile: (shader) => {
shader.uniforms.time = gu.time;
shader.uniforms.heightLimMin = { value: 0 };
shader.uniforms.heightLimMax = { value: 10 };
shader.vertexShader = `
uniform float time;
uniform float heightLimMin;
uniform float heightLimMax;
attribute vec4 particlePos;
attribute vec4 particleAlpha;
varying float vParticleAlpha;
mat2 rot(float a){float c = cos(a); float s = sin(a); return mat2(c, s, -s, c);}
${noise}
${shader.vertexShader}
`
.replace(
`#include <begin_vertex>`,
`#include <begin_vertex>
float t = time;
vParticleAlpha = sin(mod((particleAlpha.x + t * particleAlpha.y) * PI2, PI2)) * 0.5 + 0.5;
float hGap = heightLimMax - heightLimMin;
float halfGap = hGap * 0.5;
float verticalSpeed = particlePos.x;
float verticalShift = mod((position.y - heightLimMin) + verticalSpeed * t, hGap);
transformed.y = heightLimMin + verticalShift; // make it looped on Y-axis
float verticalFade = smoothstep(halfGap, halfGap - 1., abs(verticalShift - halfGap)); // for both top and bottom
vParticleAlpha *= verticalFade;
// particle shift
float n = snoise(vec4(position, t * 0.05));
float radius = particlePos.y;
float phase = particlePos.z;
float angle = (phase + n) * PI ;
vec2 shiftVec = rot(angle) * vec2(radius, 0.);
transformed.xz += shiftVec; // make it shifting
`
)
.replace(
`gl_PointSize = size;`,
`gl_PointSize = size * vParticleAlpha;`
);
//console.log(shader.vertexShader);
shader.fragmentShader = `
varying float vParticleAlpha;
${shader.fragmentShader}
`.replace(
`#include <color_fragment>`,
`#include <color_fragment>
vec2 uv = gl_PointCoord.xy - 0.5;
float d = sqrt(dot(uv, uv));
if(d > 0.5) discard;
float f = smoothstep(0.5, 0., d);
f *= f * f * f * f;
f = f * 0.95 + 0.05;
diffuseColor.a = vParticleAlpha * f;
`
);
//console.log(shader.fragmentShader);
},
});
super(g, m);
}
}
let scene = new THREE.Scene();
scene.background = new THREE.Color("maroon");
let camera = new THREE.PerspectiveCamera(
60,
innerWidth / innerHeight,
1,
1000
);
camera.position.set(0, 5, 10);
let renderer = new THREE.WebGLRenderer({ antialias: true });
renderer.setSize(innerWidth, innerHeight);
document.body.appendChild(renderer.domElement);
window.addEventListener("resize", (event) => {
camera.aspect = innerWidth / innerHeight;
camera.updateProjectionMatrix();
renderer.setSize(innerWidth, innerHeight);
});
let controls = new OrbitControls(camera, renderer.domElement);
controls.enableDamping = true;
controls.target.set(0, 5, 0);
let gu = {
time: { value: 0 },
};
let grid = new THREE.GridHelper();
scene.add(grid);
let particles = new Particles(gu);
scene.add(particles);
let clock = new THREE.Clock();
renderer.setAnimationLoop((_) => {
let t = clock.getElapsedTime();
gu.time.value = t;
controls.update();
renderer.render(scene, camera);
});
</script>
</body>
</html>
完整源码：GitHub
小结
- 本文提供 随机粒子效果 完整 Three.js 源码与在线 Demo，建议先运行案例再改 uniform/参数做二次实验
- 更多 Three.js 实战案例见 three-cesium-examples 合集 与 GitHub 开源仓库