canvas 动画

ゝ一纸荒年。 2022-12-04 01:16 146阅读 0赞

# canvas实现的动画 #

效果图：  
![在这里插入图片描述][20200904184921849.gif_pic_center]

代码：

<!DOCTYPE html>
    <html lang="en">
    <head>
    	<meta charset="UTF-8">
    	<title>Document</title>
    	<style>
    		body { 
    		  	background: #111;
    		  	padding:0;
    		  	margin:0;
    			overflow:hidden;
    		}
    	</style>
    </head>
    <body>
    	<div id="wrapper"></div>
    </body>
    <script>
    (function(){ 
    	'use strict';
    	let wrapper, canvas, ctx, width, height, 
    	Tau=Math.PI*2, PI180=Math.PI/180,
    	systems=[];
    
    /* PlanetarySystem */
    	let PlanetarySystem = function(id='pSys'){ 
    		Object.defineProperty(this, 'id',               {  value:id, writable:true} );
    		Object.defineProperty(this, 'x',                {  value:0, writable:true });
    		Object.defineProperty(this, 'y',                {  value:0, writable:true });
    		Object.defineProperty(this, 'allBodies',        {  value:[], writable:true });
    		Object.defineProperty(this, 'allBodiesLookup',  {  value:{ }, writable:true });    // fast id lookup for children
    		Object.defineProperty(this, 'numBodies',        {  value:0, writable:true });
    	}
    	PlanetarySystem.prototype.addBody = function(vo) { 
    		vo.parentSystem = this;
    		vo.parentBody = vo.parentBody === null ? this : this.allBodiesLookup[vo.parentBody];
    		let body = new PlanetaryBody(vo);
    		body.update();
    		this.allBodies.push(body);
    		this.allBodiesLookup[vo.id] = body;
    		this.numBodies += 1;
    	}
    	PlanetarySystem.prototype.setSpeedFactor = function(value){ 
    		let body;
    		for(let i=0; i<this.numBodies; i++){ 
    			body = this.allBodies[i];
    			body.setSpeedFactor(value);
    		}
    	}
    	PlanetarySystem.prototype.update = function(){ 
    		let body;
    		for(let i=0; i<this.numBodies; i++){ 
    			body = this.allBodies[i];
    			body.update();
    		}
    	}
    /* PlanetaryBody */
    	let PlanetaryBody = function(vo){ 
    		Object.defineProperty(this, 'id',					{  value:vo.id, writable:true} );
    		Object.defineProperty(this, 'diameter',				{  value:vo.diameter, writable:true });
    		Object.defineProperty(this, 'colour',				{  value:vo.colour, writable:true });
    		Object.defineProperty(this, 'x',					{  value:0, writable:true });
    		Object.defineProperty(this, 'y',					{  value:0, writable:true });
    		Object.defineProperty(this, 'vx',					{  value:0, writable:true });
    		Object.defineProperty(this, 'vy',					{  value:0, writable:true });
    		Object.defineProperty(this, 'degrees',				{  value:vo.degrees, writable:true });
    		Object.defineProperty(this, 'speedBase',			{  value:vo.speed, writable:true });
    		Object.defineProperty(this, 'speed',				{  value:vo.speed , writable:true });
    		Object.defineProperty(this, 'orbitalRadius',		{  value:vo.orbitalRadius, writable:true });
    		Object.defineProperty(this, 'parentSystem',			{  value:vo.parentSystem, writable:true });
    		Object.defineProperty(this, 'parentBody',			{  value:vo.parentBody, writable:true });
    
    		return this;
    	}
    	PlanetaryBody.prototype.update = function(){ 
    		let angle = this.degrees * PI180;
    		this.degrees += this.speed;
    		this.vx = this.orbitalRadius * Math.cos(angle);
    		this.vy = this.orbitalRadius * Math.sin(angle);
    		// update position
    		if(this.parentBody != null){ 
    			this.x = this.vx + this.parentBody.x;
    			this.y = this.vy + this.parentBody.y;
    		}
    	}
    
    /* init() */
    	function init(){ 
    		wrapper = document.querySelector('#wrapper');
    		canvas = createCanvas('canvas', width, height);
    		wrapper.appendChild(canvas);
    		ctx = canvas.getContext('2d');
    		setupEvents();
    		resizeCanvas();
    
    		/* Define new PlanetarySystem and set values */
    		let system1 = new PlanetarySystem('pSys1');
    		systems.push(system1);
    		system1.x = width * .5;
    		system1.y = height * .5;
    		system1.addBody({ id:'sun', diameter:5, degrees:0, speed:0, colour:'#FDFE1D', orbitalRadius:0, parentBody:null});
    		for(let loop=30, i=0; i<loop; i+=1){ 
    			system1.addBody({ 	id:				'ball'+i,
    								diameter:		5,
    								degrees:		0,
    								speed:			2 + (loop * 0.15) - (i* 0.2),
    								colour:			'#FDFE1D',
    								orbitalRadius:	7*(i+1),
    								parentBody:		'sun'});
    		}
    	}
    	
    /* Methods */
    	function createCanvas(id, w, h){ 
    		let tCanvas = document.createElement('canvas');
    		tCanvas.width = w;
    		tCanvas.height = h;
    		tCanvas.id = id;
    		return tCanvas;
    	}
    
    	function setupEvents(){ 
    		window.onresize = resizeCanvas;
    	}
    	function resizeCanvas(){ 
    		let rect = wrapper.getBoundingClientRect();
    		width = window.innerWidth;
    		height = window.innerHeight - rect.top -2;
    		canvas.width = width;
    		canvas.height = height;
    		for(let i=0; i<systems.length; i++){ 
    			systems[i].x = width * .5;
    			systems[i].y = height * .5;
    		}
    	}
    
    	function update(){ 
    		for(let loop=systems.length, i=0; i<loop; i++){ 
    			systems[i].update();
    		}
    	}
    
    	function draw(){ 
    		let system;
    		let prev = null;
    		for(let i=0; i<systems.length; i++){ 
    			system = systems[i];
    			let planetaryBody;
    			for(let loop=system.numBodies, j=1; j<loop; j+=1) { 
    				planetaryBody = system.allBodies[j];
    				ctx.beginPath();
    				ctx.arc(planetaryBody.x, planetaryBody.y, planetaryBody.diameter, 0, Tau, false);
    				ctx.fillStyle = planetaryBody.colour;
    				ctx.fill();
    				if(j>1){ 
    					ctx.strokeStyle = planetaryBody.colour;
    					ctx.lineWidth = 2;
    					ctx.beginPath();
    					ctx.moveTo(planetaryBody.x, planetaryBody.y);
    					ctx.lineTo(prev.x, prev.y);
    					ctx.stroke();
    				}
    				prev = { x:planetaryBody.x, y:planetaryBody.y};
    			}
    		}
    	}
    
    	function animate(){ 
    		ctx.fillStyle = 'rgba(0,0,0, .05)';
    		ctx.fillRect(0, 0, width, height);
    		update();
    		draw();
    		requestAnimationFrame(animate);
    	}
    	init();
    	animate();
    }());
    </script>
    </html>

偶然发现的canvas实现的动画，很厉害是不是

[20200904184921849.gif_pic_center]: /images/20221123/833973fad805424e8bf9b328718a4fd2.png