Custom Particles
The ability to use custom particles provides infinite flexibility in producing particle effects. Use logos, text or movie clips as custom particles.

If there are any effects or masks applied to the custom particle layer it needs to be pre-composed (Layer>Pre-Compose). If the effects are complex it is a good idea to pre-render the particle. It is recommended to keep layer size as small as possible, no larger than 200*200 pixels is recommend. The rule-of-thumb for custom particle layer size is to keep it so that the layer is the same size as the largest visible particle. If the custom particle layer is larger than that, unnecessary computations are made.

Custom particle layers must always start at the same frame as the layer Trapcode Particular is applied to.

Step-by-step instructions on using Custom Particles
We'll start by creating the particle in its own comp. If an image or movie clip is to used as custom particle, it is not necessary to create a comp for it. In this tutorial we'll use AE's text tool and in that case the particle must to be in its own comp.

Create a new comp (Ctrl/Cmd-N), make it 200*200 and 30 fps. 5 seconds long. Name it "Star".
Use the text tool, arial font, size 400px and type a star ("*"), use 30px stroke so it looks something like this:



Now it's time for the main comp where the Trapcode Particular effect is used.
Create a new comp (Ctrl/Cmd-N), make it 640*480 at 30 fps. 5 seconds long. Name it "Main".
Create a new comp-sized solid (Ctrl/Cmd-Y). Make sure to click "Make Comp Size" before OK.
Apply Effect>Trapcode>Particular to the solid.

Drag the "Star" comp from the project window into the comp window. Make sure it starts at the same frame as the particle layer.,

In Particular, set Patricle>Particle Type to Custom.
Set Particle>Custom>Layer to "Star"
Set Particle>Size to 20.
Switch both layers to high quality.
Turn off visibility for the "Star" layer.

Hit RAM preview and it should look something like this:



Colorizing Custom Particles
To colorize the custom particle, set Particle>Particle Type to "Custom Colorize".
Set Particle>Set Color to "Over Life". Now particles are colorized using Color over Life:



Also try setting Particle>Particle Type to "Custom Fill". As can be seen, this is also a colorizing mode, but instead of using lightness this mode only fills the alpha of the particle.


Time Sampling Modes
If the particle is a still, as in the example above, the Particle>Custom>Time Sampling mode should always be "Current Time" (the default). This will speed up rendering because then the same frame of the layer is used for all particles in the current frame.

When using an animated particle, the other modes are sometimes useful:
It can drastically reduce render time to pre-render the custom particle layer if using any of these modes.

Start at Birth - Play Once Plays the custom layer from start once. The particle may die before the custom layer ends, or the custom layer may end before the particle dies.
Start at Birth - Loop Plays the custom layer from start and re-starts if the layer ends.
Start at Birth - Stretch Plays the custom layer from start and time-stretches it so it ends exactly when the particle dies.
Random - Still Frame Grabs a random frame from the custom layer and uses throughout the partlicles life.
Random - Play Once Starts playing the custom layer from a random frame, and then plays at normal speed. The particle may die before the custom layer ends, or the custom layer may end before the particle dies.
Random - Loop Starts playing the custom layer from a random frame, and then plays at normal speed. If the custom layer ends, it re-starts from the beginning.

The Split Clip modes splits the custom layer into a number of clips given by the parameter "Number of Clips". For example, if the custom layer is 30 frames and "Number of Clips" is set to three, that means it will be split into three 10 frame clips. This is useful for creating a set of animated particles.

Split Clip - Play Once Randomly select one of the clips and play the clip once.
Split Clip - Loop Randomly select one of the clips and play the clip looping.
Split Clip - Stretch Randomly select one of the clips and time-stretch it to fit the particle life.