github.com/armen/terraform@v0.5.2-0.20150529052519-caa8117a08f1/website/source/assets/javascripts/app/Engine.Particle.js (about)

     1  (function(
     2  	Engine,
     3  	Vector
     4  ){
     5  
     6  Engine.Particle = function(width, height){
     7  	var side, targetX, targetY;
     8  	this.accel = Vector.coerce(this.accel);
     9  	this.vel   = Vector.coerce(this.vel);
    10  	this.pos   = new Vector(0, 0);
    11  
    12  	this.maxRadius = Engine.getRandomFloat(0.1, 2.5);
    13  	// this.maxSpeed = Engine.getRandomFloat(0.01, 1000);
    14  	this.maxSpeed = Engine.getRandomFloat(20, 1000);
    15  
    16  	// Pick a random target
    17  	side = Engine.getRandomInt(0, 3);
    18  	if (side === 0 || side === 2) {
    19  		targetY = (side === 0) ? -(height / 2) : (height / 2);
    20  		targetX = Engine.getRandomInt(-(width / 2), width / 2);
    21  	} else {
    22  		targetY = Engine.getRandomInt(-(height / 2), height / 2);
    23  		targetX = (side === 3) ? -(width / 2) : (width / 2);
    24  	}
    25  
    26  	this.target = new Vector(targetX, targetY);
    27  	this.getAccelVector();
    28  
    29  	this.maxDistance = this.distanceTo(this.target);
    30  
    31  	this.fillA = '#8750c2';
    32  	this.fillB = '#b976ff';
    33  	this.frameMax = Engine.getRandomInt(1, 5);
    34  };
    35  
    36  Engine.Particle.prototype = {
    37  
    38  	radius: 1,
    39  
    40  	frame: 0,
    41  	showA: false,
    42  
    43  	accel: {
    44  		x: 0,
    45  		y: 0
    46  	},
    47  
    48  	vel: {
    49  		x: 0,
    50  		y: 0
    51  	},
    52  
    53  	pos: {
    54  		x: 0,
    55  		y: 0
    56  	},
    57  
    58  	opacity: 1,
    59  
    60  	maxSpeed: 1500,
    61  	maxForce: 1500,
    62  
    63  	getAccelVector: function(){
    64  		this.accel = Vector.sub(this.target, this.pos)
    65  			.normalize()
    66  			.mult(this.maxSpeed);
    67  	},
    68  
    69  	update: function(engine){
    70  		var distancePercent, halfWidth, halfHeight;
    71  
    72  		this.vel
    73  			.add(this.accel)
    74  			.limit(this.maxSpeed);
    75  
    76  		this.pos.add(Vector.mult(this.vel, engine.tick));
    77  
    78  		halfWidth  = engine.width  / 2 + this.maxRadius;
    79  		halfHeight = engine.height / 2 + this.maxRadius;
    80  
    81  		if (
    82  			this.pos.x < -(halfWidth) ||
    83  			this.pos.x > halfWidth ||
    84  			this.pos.y < -(halfHeight) ||
    85  			this.pos.y > halfHeight
    86  		) {
    87  			this.kill(engine);
    88  		}
    89  
    90  		distancePercent = (this.maxDistance - this.distanceTo(this.target)) / this.maxDistance;
    91  		this.radius = Math.max(0.1, this.maxRadius * distancePercent);
    92  
    93  		this.frame++;
    94  		if (this.frame > this.frameMax) {
    95  			this.frame = 0;
    96  			this.showA = !this.showA;
    97  		}
    98  
    99  		if (this.showA) {
   100  			engine.particlesA[engine.particlesA.length] = this;
   101  		} else {
   102  			engine.particlesB[engine.particlesB.length] = this;
   103  		}
   104  
   105  		return this;
   106  	},
   107  
   108  	draw: function(ctx, scale){
   109  		if (this.radius < 0.25) {
   110  			return;
   111  		}
   112  
   113  		if (this.showA) {
   114  			ctx.fillStyle = this.fillA;
   115  		} else {
   116  			ctx.fillStyle = this.fillB;
   117  		}
   118  
   119  		// Draw a square - very performant
   120  		ctx.fillRect(
   121  			this.pos.x * scale >> 0,
   122  			this.pos.y * scale >> 0,
   123  			this.radius * scale,
   124  			this.radius * scale
   125  		);
   126  
   127  		// Draw a circle - far less performant
   128  		// ctx.beginPath();
   129  		// ctx.arc(
   130  		//     this.pos.x * scale,
   131  		//     this.pos.y * scale,
   132  		//     this.radius * scale,
   133  		//     0,
   134  		//     Math.PI * 2,
   135  		//     false
   136  		// );
   137  		// ctx.fill();
   138  
   139  		return this;
   140  	},
   141  
   142  	kill: function(engine){
   143  		engine._deferredParticles.push(this);
   144  		return this;
   145  	},
   146  
   147  	distanceTo: function(target) {
   148  		var xd = this.pos.x - target.x;
   149  		var yd = this.pos.y - target.y;
   150  		return Math.sqrt(xd * xd + yd * yd );
   151  	}
   152  };
   153  
   154  })(window.Engine, window.Vector);