特效描述：利用HTML5实现 绘制3D 线条延伸 动画特效。利用HTML5实现雷达地区扫描动画特效

代码结构

1. HTML代码

;(function() {

'use strict';

var c = document.getElementById('c');

var ctx = c.getContext('2d');

var w = c.width = window.innerWidth;

var h = c.height = window.innerHeight;

var cx = w / 2;

var cy = h / 2;

var fl = 1000;

function prj(obj) {

var cz = obj.z + fl;

if(cz === 0) return;

var scl = fl / cz;

obj.p.x = cx + obj.x * scl;

obj.p.y = cy + obj.y * scl;

obj.s = scl;

}

var P = function(x, y, z) {

this.x = x;

this.y = y;

this.z = z;

this.s = 1;

this.cl = 0;

this.p = {

x: 0,

y: 0

};

};

P.prototype = {

constructor: P,

update: function() {

this.z -= 30;

},

render: function(ctx) {

if(this.z <= -fl) return;

ctx.save();

ctx.translate(this.p.x, this.p.y);

ctx.scale(this.s, this.s);

ctx.fillStyle = 'hsla(' + this.cl + ', 100%, 50%, 0.5)';

ctx.beginPath();

ctx.arc(0, 0, 2, 0, Math.PI * 2);

ctx.fill();

ctx.restore();

}

};

var M = function(x, y, z) {

this.list = [];

this.max = 100;

this.x = x;

this.y = y;

this.z = z;

this.s = 1;

this.p = {

x: 0,

y: 0

};

this.ax = Math.random() * (Math.PI * 2);

this.ay = Math.random() * (Math.PI * 2);

this.rx = Math.random() * 100;

this.ry = Math.random() * 100;

this.cl = Math.random() * 360;

this.cls = Math.random();

};

M.prototype = {

constructor: M,

update: function() {

this.cl += this.cls;

this.ax += Math.random() * 0.1 - 0.02;

this.ay += Math.random() * 0.1 - 0.02;

this.x = Math.cos(this.ax) * 100;

this.y = Math.sin(this.ay) * 100;

this.z += 10;

if(this.z > fl) this.z = fl;

if(this.list.length < this.max) {

if(Math.random() * 100 < 50) {

var pp = new P(this.x, this.y, this.z);

pp.cl = this.cl;

this.list.push(pp);

}

} else {

var pp = this.list.shift();

pp.x = this.x;

pp.y = this.y;

pp.z = this.z;

pp.cl = this.cl;

this.list.push(pp);

}

},

render: function(ctx) {

if(this.z <= -fl) return;

ctx.save();

ctx.translate(this.p.x, this.p.y);

ctx.fillStyle = 'green';

ctx.beginPath();

ctx.arc(0, 0, 2, 0, Math.PI * 2);

ctx.fill();

ctx.restore();

}

};

function update(mv, list) {

for(var i = 0; i < list.length; i++) {

var p = list[i];

p.update();

prj(p);

p.render(ctx);

}

for(var i = list.length-1; i >= 0; i--) {

var p = list[i];

if(p.z <= -fl) continue;

if(i === list.length - 1) {

ctx.lineWidth = Math.random();

ctx.strokeStyle = 'hsl(' + mv.cl + ', 100%, 50%)';

ctx.beginPath();

ctx.moveTo(p.p.x, p.p.y);

} else {

ctx.lineTo(p.p.x, p.p.y);

}

}

ctx.stroke();

}

var ms = [];

for(var i = 0; i < 10; i++) {

ms.push(new M(

Math.random() * 400 - 200,

Math.random() * 400 - 200,

Math.random() * 400 - 200));

}

requestAnimationFrame(function loop() {

requestAnimationFrame(loop);

ctx.clearRect(0, 0, w, h);

for(var i = 0; i < ms.length; i++) {

var m = ms[i];

m.update();

prj(m);

update(m, m.list);

}

});

})();