The Particle Emitter component sprays a stream of small textured sprites into the scene. It is suited to fire, smoke, sparks, rain, snow, bubbles, dust, and magic effects. Particles are simulated in world space, so if the emitter moves it will leave a trail of particles behind it. Particle Emitters can be controlled with the Control Animation action.
Particles are spawned from the emitter with a degree of randomization, customizable by the Range fields (see below). By adjusting the range of spawn position, rotation, and velocity, you can control where particles appear and what directions they fly in. When a range value is specified, a random number between -Range and +Range will be added to the particle’s behavior when it spawns.
Also note that particles can optionally be affected by a constant force (such as gravity or wind) and by drag.
Image
The texture drawn for each particle. If left empty, a soft white dot is used.
Max Particles
The maximum number of particles that this emitter can emit at once.
Active Particles
The actual number of particles the emitter should simulate. This value can be changed at runtime to ramp particle flow up or down.
Blending
The blend mode for particles, Alpha or Additive.
Loop
If set, the emitter will continue to emit particles continuously, recycling older particles as they die off. Otherwise, the emitter will fire off the Active Particles number of particles and then stop.
Pre-warm
If set, a looping emitter starts mid-cycle. Pre-warm has no effect when Loop is off.
Rewind When Disabled
If set, the particle emitter will reset when disabled and fire its particles again when re-enabled.
Reduce Overdraw
Set this option to improve performance specifically for emitters that spew lots of overlapping particles over a large portion of the visible screen. This option lowers the resolution of the particles in order to improve rendering performance when lots of particles overlap. However, it can have negative quality and performance impacts on simpler systems, or when particles that do not cover a lot of the screen. Experiment with this option only when performance becomes an issue.
Link Spawn to Emitter
Set this to another object with a Particle Emitter to make this emitter a follow-on effect of that one. When set, this emitter does not spawn particles on its own. When a particle on the linked emitter dies, this emitter will spawn a new particle in the same place.
Lifetime / Lifetime Range
How long, in seconds, a particle lives before it respawns.
Spawn Range X / Spawn Range Y
How far from the emitter’s position particles may appear. Use these to spread the source of the effect over an area rather than a point. These values are ignored on emitters that have their spawner linked to another emitter (see Link Spawn to Emitter, above).
Velocity X / Velocity Y
The speed, in pixels per second, that a particle starts with.
Velocity Range X / Velocity Range Y
The range of velocities that may be added to a new particle’s velocity at spawn time.
Force X / Force Y
A constant acceleration applied to every particle, in pixels per second squared. A negative Force Y pulls particles down like gravity, and a positive Force Y makes them rise.
Drag
Slows particles over time.
Rotation
The angle, in degrees, a particle starts at.
Rotation Range
The range of angles to randomly add to the rotation of a new particle when it spawns.
Spin
How fast a particle rotates, in degrees per second.
Spin Range
The range of additional rotational speed to randomly add to particles when they spawn.
Scale
A multiplier on the size of the particle’s image. When no image is set, the built-in soft dot is 32 x 32 pixels.
Scale Range
The range of scale adjustments to randomly apply to new particles when they spawn.
Scale Rate
How fast a particle grows or shrinks, in multiples of its image size per second. Negative values shrink.
Color
Particles fade from a start color to an end color over their lifetime. Setting the end color’s alpha to zero makes particles fade out as they age instead of vanishing abruptly.
Optional colors that a particle passes through on its way from the start and end colors may be added by clicking the + button. Colors may be dragged around to reorder them. Drag a color out and drop it elsewhere to remove it from the list.