ParticleKit

A 2D particle system.

Installation

Add the following to your Cartfile:

github "mattcomi/ParticleKit"

Usage

Import the framework:

import ParticleKit

Create a ParticleSystem:

let system = ParticleSystem(size: 1024)

The capacity parameter specifies how many particles may exist at any one time. An existing particle will be replaced if a particle is emitted beyond this capacity.

The color and size of particles may vary during their lifetime. Specify these values using Gradient objects:

let colorGradient = Gradient<UIColor>()

colorGradient.add(location: 0, value: UIColor(red: 1, green: 0, blue: 0, alpha: 1))
colorGradient.add(location: 0.5, value: UIColor(red: 0, green: 1, blue: 0, alpha: 1))
colorGradient.add(location: 1, value: UIColor(red: 0, green: 0, blue: 1, alpha: 0))

let sizeGradient = Gradient<CGFloat>()

sizeGradient.add(location: 0, value: 0)
sizeGradient.add(location: 0.3, value: 1)
sizeGradient.add(location: 0.6, value: 0.5)
sizeGradient.add(location: 1.0, value: 0)

And assign them to the ParticleSystem:

system.colorGradient = colorGradient
system.sizeGradient = sizeGradient

Specify the physical properties of particles using a ParticleSystemProperties object:

var properties = ParticleSytemProperties()

properties.position = ParticleSystemValue(origin: .zero, spread: .zero)
properties.lifetime = ParticleSystemValue(origin: 25, spread: 0)
properties.linearVelocityAngle = ParticleSystemValue(origin: Angle(degrees: 270), spread: Angle(degrees: 5))
properties.linearVelocitySpeed = ParticleSystemValue(origin: 4, spread: 0)
properties.angle = ParticleSystemValue(origin: Angle(degrees: 0), spread: Angle(degrees: 360))
properties.angularVelocity = ParticleSystemValue(origin: Angle(degrees: 0), spread: Angle(degrees: 8))

And assign it to the ParticleSystem:

system.properties = properties

Emit a particle!

system.emit()

Update the ParticleSystem:

system.update()

Note that the time unit is updates. In other words, a lifetime of 25 specifies 25 calls to update(). Similarly, an angular velocity of 10 degrees indicates that the particle rotates 10 degrees each update.

And finally, render the particles:

for particle in particleSystem.particles {
  let quad = particle.quad
  let color = particle.color
  
  // draw the quad
}