Emission and Shapes

Shape, direction, and emission rate combine into the distribution visible in the live Scene.

Emission decides when to spawn particles. Shape decides where they start and which direction supplies their initial speed.

Emission Sources

Source	Behaviour
Emission Rate	Spawn continuously over emitter time.
Distance Rate	Spawn as the emitter travels, useful for footsteps and moving trails.
Burst	Spawn a configured count at a specific cycle time.

Bursts include time, count, cycles, interval, and probability. The emitter tracks each burst cycle so looping emitters do not replay old burst state incorrectly.

Shape Transform

The Shape module adds its own position, rotation, and scale inside the emitter transform. This is useful when the visual emission volume needs a different pivot without adding another Empty object.

Built-in Shapes

Shape	Important controls	Typical use
Dot	none	One origin point.
Box	dimensions and emit-from mode	Volumes, planes, or box surfaces.
Circle	radius, thickness, arc	Rings and radial sprays.
Cone	angle, radius, thickness, arc	Fire, jets, and directional spreads.
Cylinder	radius, thickness, arc	Columns and circular walls.
Sphere	radius, thickness, arc	Explosions, auras, and shells.
Mesh	vertices, edges or triangles of a mesh source	Emit from authored model geometry.
Function	expressions for position/direction	Procedural paths and mathematical volumes.

Arc

Circle-like shapes can restrict their angular range and choose how that range is traversed. Arc modes provide random distribution or ordered progression; loop, ping-pong, spread, and speed controls determine how emission advances.

Radius Thickness

A thickness of 0 emits on the outer surface. Larger values allow points further toward the center. Use a shell for readable outlines and a filled volume for clouds or explosions.

Mesh Sources

Universal mesh sources since 2.2.0

Mesh shapes use the same sources as Model rendering: built-in primitives, OBJ Model, Json Model, glTF Model, Animated glTF Model, or a Mesh Reference to a reusable Mesh resource. This avoids maintaining separate shape and renderer meshes. See Mesh Sources for the full list.

glTF Model since 2.2.5 Animated glTF Model since 2.2.7

A glTF Model works like any other mesh. With an Animated glTF Model, the shape follows the animation: particles spawn on the current shared-clock pose, even when the model uses Per-Particle Phase for rendering. The sampling weights (edge lengths and triangle areas) stay those of the rest pose, so a stretched limb gets its unstretched share. See glTF Models.

Ground Snap

Since 2.2.9

Since 2.2.9, Ground Snap drops every spawn point onto the terrain below it. Use it for dust, debris or grass tufts that should start on the ground under an emitter that floats above it. Turn on Ground Snap in the Particle Emitter's Shape module.

Each new particle looks for ground along a straight line from its spawn point and moves onto the first surface it hits.

Option	Default	Description
Direction	WorldDown	WorldDown: straight down. EmitterDown: the emitter's -Y, for emitters on walls and ceilings.
Max Distance	8 (0–256)	How far below the spawn point to look for ground, in blocks.
Search Above	1 (0–64)	Start looking this far above the spawn point, so points just under the surface still find it.
Offset	0 (-16–16)	Distance from the surface along its normal.
Include Fluids	off	Land on fluid surfaces too.
Align To Normal	off	Turns the start velocity so that what the shape aims up leaves the surface along its normal. It matters when the face the search lands on is not square to the search direction, for example with EmitterDown on a tilted emitter.
Discard Without Ground	off	Removes particles that find no ground within reach, instead of leaving them where the shape put them.

• The search hits block collision shapes, so slabs and stairs count, and blocks without collision (grass, flowers) do not. Collider objects are not hit.
• When the search starts inside a block (under a low ceiling, inside a tree), it searches again from the spawn point itself.
• The snap happens once, at spawn. To keep particles on the ground afterwards, use Collision.

Function Shape

Function Shape evaluates expressions for position and direction. Keep expressions deterministic and guard divisions/square roots against invalid values; a NaN spawn position cannot be rendered or collided safely.