Mr. Doc

Enjin

Particle

method
 particle.Particle() 

Option name Type Description
Options Object

Object with options you need (look at source for all availible)

Creates a particle to be spawned by an Emitter

particle.Particle = function(options) {
	// If we're passed an update function use that
	if(options.update) {
		this.updateFunc = options.update;
	}
	else {
		this.lifeTimeVariance = options.lifeTimeVariance || 0;
		this.lifeTime = (options.lifeTime || options.life || 5) + (options.lifeTime || options.life || 5) * enjin.util.randomDecimal(-this.lifeTimeVariance, this.lifeTimeVariance);
		this.isAlive = true;
		this.elapsedTime = 0;

		this.direction = enjin.util.randomDecimal(options.mindirection, options.maxdirection);
		this.directionCos = Math.cos(this.direction);
		this.directionSin = Math.sin(this.direction);

		// Linear position
		this.x = options.x || 0;
		this.y = options.y || 0;
		this.velx = (options.velx || options.vel || 0) * this.directionCos;
		this.vely = (options.vely || options.vel || 0) * this.directionSin;
		this.velVariance = options.velVariance || options.variance || 0.005;
		this.accelx = (options.accelx || options.accel || 0) * this.directionCos;
		this.accely = (options.accely || options.accel || 0) * this.directionSin;
		this.accelVariance = options.accelVariance || options.variance || 0.005;
	}

	// Drawing
	this.drawFunc = options.draw || function(ctx) { ctx.fillRect(this.x, this.y, 10, 10); }
}

update

method
 particle.Particle.prototype.update() 

Option name Type Description
DeltaTime Number

Time since last update

Update a Particle's position

particle.Particle.prototype.update = function(dt) {
	this.accelx += this.accelx * enjin.util.randomDecimal(-this.accelVariance, this.accelVariance);
	this.accely += this.accely * enjin.util.randomDecimal(-this.accelVariance, this.accelVariance);
	this.velx += this.accelx * dt;
	this.vely += this.accely * dt;
	this.velx += this.velx * enjin.util.randomDecimal(-this.velVariance, this.velVariance);
	this.vely += this.vely * enjin.util.randomDecimal(-this.velVariance, this.velVariance);
	this.x += this.velx * dt;
	this.y += this.vely * dt;

	this.elapsedTime += dt;
	if(this.elapsedTime >= this.lifeTime) {
		this.isAlive = false;
	}
}

draw

method
 particle.Particle.prototype.draw() 

Draw a single particle

particle.Particle.prototype.draw = function() {
	this.drawFunc(enjin.ctx);
}

Emitter

method
 particle.Emitter() 

Option name Type Description
X Number

X coordinate to spawn particles at
Y Number

Y coordinate to spawn particles at
ParticleOptions Object

Particle options to spawn particle with
Direction Number

The angle to send the particles off at
Spread Number

Angle of spread for the particles

Creates an Emitter to spawn Particles

particle.Emitter = function(x, y, particleOptions, maxAlive, spawnRate, direction, spread) {
	this.x = x;
	this.y = y;

	this.maxAlive = maxAlive;
	this.aliveParticles = [];
	this.spawnRate = 1 / (spawnRate || this.maxAlive / (particleOptions.lifeTime || particleOptions.life || 5));
	this.timeSinceLastSpawn = 0;

	this.particleOptions = particleOptions;
	this.particleOptions.x = x;
	this.particleOptions.y = y;

	this.direction = direction || 0;
	this.spread = spread || Math.PI;
	this.particleOptions.mindirection = this.direction - this.spread / 2;
	this.particleOptions.maxdirection = this.direction + this.spread / 2;
}

update

method
 particle.Emitter.prototype.update() 

Option name Type Description
DeltaTime Number

Time since last update

Update an Emitter's particles

particle.Emitter.prototype.update = function(dt) {
	this.timeSinceLastSpawn += dt;

	// Update position and kill
	for(var i=0; i<this.aliveParticles.length; i++) {
		this.aliveParticles[i].update(dt);
		
		if(!this.aliveParticles[i].isAlive) {
			this.aliveParticles.splice(i, 1);
		}
	}	

	// Spawn new Particles
	while(this.timeSinceLastSpawn > this.spawnRate && this.aliveParticles.length < this.maxAlive) {
		this.aliveParticles.push(new enjin.particle.Particle(this.particleOptions));
		this.timeSinceLastSpawn -= this.spawnRate;
	}
}

draw

method
 particle.Emitter.prototype.draw() 

Draw an Emitter's particles

particle.Emitter.prototype.draw = function() {
	for(var i=0; i<this.aliveParticles.length; i++) {
		this.aliveParticles[i].draw();
	}
}

// A pulse is a single "burst" of particles

Pulse

method
 particle.Pulse() 

Option name Type Description
X Number

X coordinate to spawn particles at
Y Number

Y coordinate to spawn particles at
ParticleOptions Object

Particle options to spawn particle with
NumberToSpawn Number

Total number of particles to spawn
Direction Number

The angle to send the particles off at
Spread Number

Angle of spread for the particles

Creates a pulse to spawn a group of particles

particle.Pulse = function(x, y, particleOptions, numberToSpawn, direction, spread) {
	this.x = x;
	this.y = y;

	this.numberToSpawn = numberToSpawn;
	this.particles = [];

	this.particleOptions = particleOptions;
	this.particleOptions.x = x;
	this.particleOptions.y = y;

	this.direction = direction || 0;
	this.spread = spread || Math.PI;
	this.particleOptions.mindirection = this.direction - this.spread / 2;
	this.particleOptions.maxdirection = this.direction + this.spread / 2;

	// Init particles
	for(var i=0; i<this.numberToSpawn; i++) {
		this.particles.push(new enjin.particle.Particle(this.particleOptions));
	}
}

update

method
 particle.Pulse.prototype.update() 

Option name Type Description
DeltaTime Number

Time since last update

Update a Pulse's particles

particle.Pulse.prototype.update = function(dt) {
	for(var i=0; i<this.particles.length; i++) {
		this.particles[i].update(dt);

		if(!this.particles[i].isAlive) {
			this.particles.splice(i, 1);
		}
	}
}

draw

method
 particle.Pulse.prototype.draw() 

Draw an Pulse's particles

particle.Pulse.prototype.draw = function() {
	for(var i=0; i<this.particles.length; i++) {
		this.particles[i].draw();
	}
}


// N.B. While you can make particles yourself, I'd reccomend using the library calls instead.
module.exports = particle;