Particles
A particle emitter is a layer. Insert one from the Insert menu, or add the Particles operator from Style → Shape effects → + Add.
Parameters
| Parameter | Controls |
|---|---|
| Rate | Particles emitted per second |
| Lifetime | How long each particle lives |
| Velocity | Initial speed and direction |
| Gravity | Constant acceleration |
| Turbulence | Noise-driven displacement over the field |
| Size over life | How a particle scales as it ages |
| Colour over life | How it tints as it ages |
Every numeric field is keyframeable, stored under particle.<key>, with colours
written as channel tracks. So the emitter’s rate, gravity and turbulence can all
animate — a burst is a rate spike, not a separate emitter.
Determinism
The emitter is deterministic: the same frame always produces the same field.
That is not a detail. It means:
- An export is reproducible. Render twice, get identical files.
- A re-render after a crash resumes identical work rather than producing a different-looking second half.
- Scrubbing backwards shows the truth. The field at frame 120 is the same whether you arrived there by playing forward or by dragging the playhead.
- The pixel-comparison test harness can test particles at all, which a wall-clock-seeded emitter could not be.
It follows from the same rule as the rest of the render path: frame time is
index / fps, never wall-clock. See Determinism.
Practical recipes
A burst. Keyframe rate from 0 to a high value for two or three frames, then back to 0. Give the particles a short lifetime and high initial velocity.
Ambient drift. Low rate, long lifetime, low velocity, a little turbulence, gravity at or near zero. Fade with colour-over-life rather than opacity keyframes so each particle fades on its own schedule.
Falling. Emit across the top of the frame, positive gravity, lifetime long enough to cross the composition. Add turbulence so they do not fall in parallel lines.
Cost
Particles are the most expensive thing in the app to render. If the viewport becomes sluggish:
- Turn on Draft 3D if the scene is 3D.
- Turn the FPS meter on in the status bar to see what you are actually getting.
- Reduce rate while animating and raise it before the final render — it is a keyframeable parameter, so remember to check the keys before exporting.