js实现3D粒子酷炫动态旋转特效

vars.ctx.globalAlpha=.15;
 vars.ctx.fillStyle="#000";
 vars.ctx.fillRect(0, 0, canvas.width, canvas.height);
 
 drawFloor(vars);
 
 var point,x,y,z,a;
 for(var i=0;i<vars.points.length;++i){
 x=vars.points[i].x;
 y=vars.points[i].y;
 z=vars.points[i].z;
 point=project3D(x,y,z,vars);
 if(point.d != -1){
 vars.points[i].dist=point.d;
 size=1+vars.points[i].radius/(1+point.d);
 d=Math.abs(vars.points[i].y);
 a = .8 - Math.pow(d / (vars.vortexHeight/2), 1000) * .8;
 vars.ctx.globalAlpha=a>=0&&a<=1?a:0;
 vars.ctx.fillStyle=rgb(vars.points[i].color);
 if(point.x>-1&&point.x<vars.canvas.width&&point.y>-1&&point.y<vars.canvas.height)vars.ctx.fillRect(point.x-size/2,point.y-size/2,size,size);
 }
 }
 vars.points.sort(sortFunction);
}

function spawnParticle(vars){

var p,ls;
 pt={};
 p=Math.PI*2*Math.random();
 ls=Math.sqrt(Math.random()*vars.distributionRadius);
 pt.x=Math.sin(p)*ls;
 pt.y=-vars.vortexHeight/2;
 pt.vy=vars.initV/20+Math.random()*vars.initV;
 pt.z=Math.cos(p)*ls;
 pt.radius=200+800*Math.random();
 pt.color=pt.radius/1000+vars.frameNo/250;
 vars.points.push(pt);
}

function frame(vars) {

if(vars === undefined){
 var vars={};
 vars.canvas = document.querySelector("canvas");
 vars.ctx = vars.canvas.getContext("2d");
 vars.canvas.width = document.body.clientWidth;
 vars.canvas.height = document.body.clientHeight;
 window.addEventListener("resize", function(){
 vars.canvas.width = document.body.clientWidth;
 vars.canvas.height = document.body.clientHeight;
 vars.cx=vars.canvas.width/2;
 vars.cy=vars.canvas.height/2;
 }, true);
 vars.frameNo=0;

vars.camX = 0;
 vars.camY = 0;
 vars.camZ = -14;
 vars.pitch = elevation(vars.camX, vars.camZ, vars.camY) - Math.PI / 2;
 vars.yaw = 0;
 vars.cx=vars.canvas.width/2;
 vars.cy=vars.canvas.height/2;
 vars.bounding=10;
 vars.scale=500;
 vars.floor=26.5;

vars.points=[];
 vars.initParticles=2000;
 vars.initV=.01;
 vars.distributionRadius=800;
 vars.vortexHeight=25;
 }

vars.frameNo++;
 requestAnimationFrame(function() {
 frame(vars);
 });

process(vars);
 draw(vars);
}
frame();

</script>
 </BODY>
</HTML>

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