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<html>
<body>
<canvas></canvas>
</body>
</html>
@import "compass/css3";
body,html {
margin:0;
padding:0;
}
canvas {
background-color: #0a0a0a;
}
"use strict";
var canvas = document.querySelector('canvas');
var ctx = canvas.getContext('2d');
canvas.height = window.innerHeight;
canvas.width = window.innerWidth;
var midX = canvas.width/2;
var midY = canvas.height/2;
var particleNum = 10000;
var emissionRate = 10;
var particleSize = 1.7;
var objectSize = 3; // drawSize of emitter/field
var bigG = 1;
/* Vector Class
********************/
function Vector(x, y) {
this.x = x || 0;
this.y = y || 0;
}
Vector.prototype.add = function(v) {
this.x += v.x;
this.y += v.y;
};
Vector.prototype.getMagnitude = function() {
return( Math.sqrt((this.x*this.x) + (this.y*this.y)) );
};
Vector.prototype.getAngle = function() {
return Math.atan2(this.y, this.x);
};
Vector.fromAngle = function(angle, magnitute) {
return new Vector(magnitute*Math.cos(angle), magnitute*Math.sin(angle));
}
/* Particle Class
********************/
function Particle (point, velocity, acceleration) {
this.position = point || new Vector(0,0);
this.velocity = velocity || new Vector(0,0);
this.acceleration = acceleration || new Vector(0,0);
this.color = 'rgb(0, 0, 255)';
}
Particle.prototype.calculateForces = function(fields) {
var totalAccelerationX = 0;
var totalAccelerationY = 0;
for (var i = 0; i < fields.length; i++) {
var field = fields[i];
var diff_x = field.position.x - this.position.x;
var diff_y = field.position.y - this.position.y;
var force = bigG*field.mass/Math.pow( diff_x*diff_x + diff_y*diff_y , 1.5);
totalAccelerationX += diff_x*force;
totalAccelerationY += diff_y*force;
};
this.acceleration = new Vector(totalAccelerationX, totalAccelerationY);
};
Particle.prototype.move = function() {
//Add current acceleration to current velocity
this.velocity.add(this.acceleration);
//Add current velocity to current position
this.position.add(this.velocity);
};
Particle.prototype.draw = function() {
ctx.fillStyle = this.color;
ctx.fillRect(this.position.x, this.position.y, particleSize, particleSize);
};
/* Emitter Class
********************/
function Emitter (point, velocity, spread) {
this.position = point; // Vector
this.velocity = velocity; // Vector
this.spread = spread || Math.PI / 32;
this.drawColor = "#999";
}
Emitter.prototype.emitParticle = function() {
var angle = this.velocity.getAngle() + this.spread - (Math.random()*this.spread*2);
var magnitute = this.velocity.getMagnitude();
var position = new Vector(this.position.x, this.position.y)
var velocity = Vector.fromAngle(angle, magnitute)
return new Particle(position, velocity);
};
/* Field Class
********************/
function Field(point, mass) {
this.position = point;
this.setMass(mass);
}
Field.prototype.setMass = function(mass) {
this.mass = mass || 100;
this.drawColor = mass < 0 ? "#f00" : "#0f0";
}
/* Updating Functions
********************/
function addParticles () {
if (particles.length > particleNum) {return};
for (var i = 0; i < emitters.length; i++) {
for (var j = 0; j < emissionRate; j++) {
particles.push(emitters[i].emitParticle());
};
};
}
function plotParticles (boundsX, boundsY) {
// Hold particles within bounds
var currentParticles = [];
for (var i = 0; i < particles.length; i++) {
var particle = particles[i];
var x = particle.position.x;
var y = particle.position.y;
if(x < 0 || x > boundsX || y < 0 || y > boundsY) continue;
// Calculate the forces that will affect acceleration and therefore velocity before moving particle
particle.calculateForces(fields);
particle.move();
// add this particle to current particles
currentParticles.push(particle);
}
// Update global particles
particles = currentParticles;
}
/* Drawing Functions
********************/
function drawParticles () {
for (var i = 0; i < particles.length; i++) {
particles[i].draw();
};
}
/* Misc Utilities */
function drawCircle(object) {
ctx.fillStyle = object.drawColor;
ctx.beginPath();
ctx.arc(object.position.x, object.position.y, objectSize, 0, Math.PI * 2);
ctx.closePath();
ctx.fill();
}
/* Variables that use classes defined
* above placed here due to hoisting
*************************************/
var particles = [];
var emitters = [
new Emitter(new Vector(midX - 150, midY), Vector.fromAngle(6, 2), Math.PI)
];
var fields = [
new Field(new Vector(midX - 450, midY + 20), 900),
new Field(new Vector(midX - 300, midY + 10), -90),
new Field(new Vector(midX + 300, midY - 20), 1500),
new Field(new Vector(midX + 200, midY - 10), -200),
];
/* Loop Sequence */
function loop() {
clear();
update();
draw();
queue();
}
function clear() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
}
function update() {
addParticles();
plotParticles(canvas.width, canvas.height);
}
function draw() {
drawParticles();
fields.forEach(drawCircle);
emitters.forEach(drawCircle);
}
function queue() {
window.requestAnimationFrame(loop);
}
loop();
Also see: Tab Triggers