ThreeJS+WebGL实现3D蝌蚪飞线功能

利用shader粒子做出了我心心念念的蝌蚪状飞线

先说说思路，第一步是制作一个蝌蚪状的粒子束，其实很简单就是让粒子一个一个从小到大排列就好，这部分主要利用shader处理，代码如下：

const vs:string = `

attribute float size; // 顶点尺寸

attribute vec4 colors; //顶点颜色

varying float opacity; // 控制透明度

varying vec3 vexColor; // 顶点颜色

void main(){
vexColor.x = colors.r;

vexColor.y = colors.g;

vexColor.z = colors.b;

//w分量为透明度

opacity = colors.w;

vec4 mvPosition = modelViewMatrix * vec4(position,1.0); //?这里模型矩阵，坐标向量，和投影矩阵都是three给你注入的好像。

gl_PointSize = size;

gl_Position = projectionMatrix * mvPosition;

}

`;

然后就是配置数据源，数据源可以利用three.js 给的curve3组件中的getPoints取得，代码如下

this.spline = new THREE.CatmullRomCurve3(vecs);

this.pointNum = num;

this.distance = this.spline.getLength();

//初始化粒子

this.points = this.spline.getPoints(num);

const colorsLen = this.points.length * 4;

const sizeLen = this.points.length;

const colors:Float32Array = new Float32Array(colorsLen);

const sizes:Float32Array = new Float32Array(sizeLen);

this.geometry = new THREE.BufferGeometry().setFromPoints(this.points);

for(let i=0,z=0;i<colorsLen;i+=4,z++){
//color

colors[i] = color.r;

colors[i+1] = color.g;

colors[i+2] = color.b;

// opacity

colors[i+3] = (i+3)/sizeLen;

// size从小到大

sizes[z] =size*(z/sizeLen);

};

this.geometry.addAttribute(‘colors’,new THREE.BufferAttribute(colors,4));

this.geometry.addAttribute(‘size’,new THREE.BufferAttribute(sizes,1));

第二部分就是如何让粒子运动起来，这里我借助了tween.js，整体思路就是取一段固定的粒子数目+加上Curve3的getPointAt取点函数，不断的取出固定数目并不断前移的坐标，直接修改bufferGeometry的position数据即可。

下面贴出完整代码：

import * as THREE from “three”;

import TWEEN from “@tweenjs/tween.js”;

const fs:string = `

uniform sampler2D texture;

varying float opacity;

varying vec3 vexColor;

void main(){
gl_FragColor = vec4(vexColor,opacity);

gl_FragColor = gl_FragColor * texture2D(texture,gl_PointCoord);

}

`;

const vs:string = `

attribute float size;

attribute vec4 colors;

varying float opacity;

varying vec3 vexColor;

void main(){
vexColor.x = colors.r;

vexColor.y = colors.g;

vexColor.z = colors.b;

//w分量为透明度

opacity = colors.w;

vec4 mvPosition = modelViewMatrix * vec4(position,1.0);

gl_PointSize = size;

gl_Position = projectionMatrix * mvPosition;

}

`;

/**

* 粒子飞线

*/

export default class PointsFlyLine{
//粒子位置

geometry: THREE.BufferGeometry;

//曲线

spline: THREE.CatmullRomCurve3;

//粒子系统

particleSystem: THREE.Points;

//粒子数目

pointNum:number;

//粒子间的总距离

distance: number;

points: THREE.Vector3[];

tween: any;

/**

* 创建粒子系统

* @param points 粒子

* @param size 粒子大小

* @param num 粒子数目

* @param color 粒子颜色

*/

constructor({ vecs, num, size, color }: { vecs: THREE.Vector3[]; num: number; size: number; color: THREE.Color; }){
this.spline = new THREE.CatmullRomCurve3(vecs);

this.pointNum = num;

this.distance = this.spline.getLength();

//初始化粒子

this.points = this.spline.getPoints(num);

const colorsLen = this.points.length * 4;

const sizeLen = this.points.length;

const colors:Float32Array = new Float32Array(colorsLen);

const sizes:Float32Array = new Float32Array(sizeLen);

this.geometry = new THREE.BufferGeometry().setFromPoints(this.points);

for(let i=0,z=0;i<colorsLen;i+=4,z++){
//color

colors[i] = color.r;

colors[i+1] = color.g;

colors[i+2] = color.b;

// opacity

colors[i+3] = (i+3)/sizeLen;

// size从小到大

sizes[z] =size*(z/sizeLen);

};

this.geometry.addAttribute(‘colors’,new THREE.BufferAttribute(colors,4));

this.geometry.addAttribute(‘size’,new THREE.BufferAttribute(sizes,1));

const uniforms:object = {
texture: {
value: new THREE.CanvasTexture(this.createSpriteCanvas(size)),

}

};

const shaderMaterial:THREE.ShaderMaterial = new THREE.ShaderMaterial({
uniforms,

vertexShader:vs,

fragmentShader:fs,

transparent:true,

depthTest:false

});

this.particleSystem = new THREE.Points(this.geometry,shaderMaterial);

}

//飞线开始

start(){
const max = this.distance*10;

const end:number = this.pointNum;

const m = {start:0,end};

this.tween = this.tweenAnimate(m,{start:max-end,end:max},2000,null,()=>{
let pointArr:number[] = [];

let s = Math.round(m.start),e = Math.floor(m.end);

for (let i = s; i <= e && i<=max; i++) {
pointArr = pointArr.concat(this.spline.getPointAt(i/max).toArray());

}

this.geometry.attributes.position = new THREE.BufferAttribute(new Float32Array(pointArr),3);

});

this.tween.repeat(Infinity).start();

}

stop(){
this.tween.stop();

}

tweenAnimate(current:object, target:object, interval:number, animation?:TWEEN.Easing, onUpdate?:Function, complete?:Function) {
var animate = animation ? animation : TWEEN.Easing.Linear.None;

let tween = new TWEEN.Tween(current).to(target, interval).easing(animate);

onUpdate && tween.onUpdate(() => onUpdate());

complete && tween.onComplete(() => complete());

return tween;

}

//创建圆形精灵贴图

createSpriteCanvas(size:number){
const canvas = document.createElement(‘canvas’);

canvas.width = canvas.height = size;

const context = canvas.getContext(‘2d’);

if(context!=null){
context.fillStyle=’rgba(255,255,255,.0)’;

context.beginPath();

context.arc(size/2,size/2,size/2,0,Math.PI*2);

context.fillStyle = ‘white’;

context.fill();

context.closePath();

}

return canvas;

}

}
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版权声明：本文为CSDN博主「lyh1995a」的原创文章，遵循CC 4.0 BY-SA版权协议，转载请附上原文出处链接及本声明。
原文链接：https://blog.csdn.net/qq_22939353/article/details/99691224