Particles
A particle emitter gives you fire, smoke, sparks, dust, rain, magic — anything made of many small things moving together.
Particles are born on a shape, fly under gravity and drag, and fade out over their lifetime. All of it runs on the GPU and draws in a single call, so a thousand particles cost roughly what one sprite does.
The defaults are a fire preset, so you can add an emitter and immediately see what you are tuning rather than staring at an empty object.
How many, and for how long
| Setting | Does |
|---|---|
count | how many particles exist at once |
lifetime | how many seconds each one lives |
emitting | switch the emitter on and off |
The spawn rate falls out of these two: count ÷ lifetime particles per second. A short
lifetime with a high count gives you a dense, fast effect; a long lifetime with the same count
gives you a slow, sparse one.
Where they are born
shape | Particles start… |
|---|---|
point | all from one spot |
sphere | anywhere within radius |
box | anywhere within extents |
cone | in a cone around the object's up axis, width by angle |
angle is a half-angle in degrees, so 15 is a tight jet and 180 sprays in every direction.
Cone is the default because it suits fire, jets, sparks and fountains alike.
How they move
| Setting | Does |
|---|---|
speedMin · speedMax | starting speed, picked between the two |
gravity | constant pull — negative Y for falling, positive for rising |
drag | how quickly they slow down |
turbulence | how much they wander; this is what stops smoke looking mechanical |
spin | rotation speed |
The default preset pulls particles upward — that is what makes fire and smoke rise. Sideways gravity gives you wind-blown rain or a spray in a draught.
How they look
| Setting | Does |
|---|---|
sizeStart · sizeEnd | size at birth and at death |
sizeJitter | how much sizes vary between particles |
colorStart · colorEnd | colour over the lifetime |
opacityStart · opacityEnd | fade in and out |
sprite | an image; its transparency gives the particle shape |
blending | additive or normal |
Blending is the setting that decides whether an effect reads as light or as matter.
additive accumulates brightness where particles overlap — fire, sparks, magic, anything
glowing. normal layers them like paint — smoke, dust, rain, debris.
Without a sprite you get a soft circle, which is genuinely fine for smoke and sparks.
A few starting points
| Effect | Roughly |
|---|---|
| Fire | cone, narrow angle, upward gravity, additive, yellow to red, shrinking |
| Smoke | cone, wide angle, gentle upward gravity, normal blending, grey, growing, fading out |
| Sparks | point or cone, high speed, downward gravity, additive, tiny, short lifetime |
| Dust | box, near-zero speed, no gravity, high turbulence, normal blending, long lifetime |
| Rain | box overhead, downward gravity, high speed, low turbulence |
Everything is a setting, nothing is state
No particle is ever stored or synchronised. The same settings produce the same look for every viewer, which means an emitter costs nothing to have in a multiplayer scene and never drifts out of step between participants.
The seed controls the randomness: change it for a different arrangement from the same
settings, keep it and everyone sees the same one.
Next: Cameras — what your visitor is looking through.