Particle Layers

Particle layers are a way to simulate such effects as flowing water, fire, bubbles, or other effects that you can imagine are made up of many small objects. A particle layer is like a group layer in that it can contain sub-layers. However, instead of just displaying its sub-layers as they are, a particle layer will automatically animate its sub-layers so that they appear to be flowing outward from the particle layer's origin.

The direction that a particle layer sprays its particles is illustrated below.

Particle spray direction.

During an animation, a particle layer can be turned on or off. When it is turned off, no more particles will be created, but those that already exist will continue to the end of their lifetime. To turn a particle layer on or off, right-click its entry in the Layers panel. A popup menu will appear to let you turn the particle layer on or off.

The complete list of settings for a particle layer is as follows. These settings are accessible in the Layer Properties dialog, under the "Particles" tab:

• Particle count - the total number of particles visible at any one time
• Preview particles - the number of particles displayed in the working view (a smaller number than "Particle count" keeps the working view from slowing down too much)
• Lifetime - the number of frames before a particle is "recycled" and sent back to the source. If set to zero, the particles will keep going for the duration of the animation.
• Source width - the width of the spray source
• Source height - the height of the spray source
• Source depth - the depth of the spray source. If set to a number greater than zero, then some particles will appear closer to the camera than others.
• Velocity - the speed that particles start at (a value of 2 will cause a particle to cross the entire screen vertically in one second)
• Velocity spread - amount of random variation in the particles' velocity
• Damping - this acts kind of like "air resistance", or backwards acceleration
• Direction - an angle indicating direction to spray particles in (see above figure)
• Spread - how wide the spray should be (see above figure) (a value of 360 will cause particles to spray in all directions)
• Acceleration - the direction of acceleration (straight down simulates gravity)
• Rate - the rate of acceleration
• On at start - whether the particle layer should be on at the start of the animation
• Full speed start - if the layer is on, this checkbox indicates if it should be running at "full speed", or just starting
• Orient particles - if checked, then the particles will rotate to face the direction they're moving in
• Free-floating - if un-checked, then the particles will be tied to the particle layer if it is moved
• Evenly spaced - if checked, then the particles will be released in even time increments
• Randomize playback - normally, particles will start their animation from the beginning when they are first created. If this box is checked, then particles will start playback at a random time. This is useful when simulating things like crowds of people (see the Tutorials section).