Particle initializers

IntermediateArtistProgrammer Initializers control the states of particles such as position, velocity, size, and so on when the particles are first spawned. They have no effect on particles spawned on previous frames.

Note

updaters act change the particle’s value at the end of the frame. They effectively overwrite any initial values set by a similar initializer. Such is the case with all animations. They operate on the particle’s lifetime and a color animation updater will overwrite any initial values from a color initializer. Similarly, initializers which operate on the same field are exclusive and only the bottom one will have any effect, since they are executed in order. For example if you assign two color initializer, only the second one will have any effect.]

Common properties

Several properties are common across many initializers. For example, a velocity initializer can change its direction depending on the parent’s rotation or decide to ignore it and always shoot particles in a fixed direction. On the other hand, size initializers don’t change based on the parent’s rotation, so the rotation fields won’t appear at all.

Position

Particles are spawned in an axis-aligned bounding box, defined by its left lower back corner and its right upper front corner. This image shows the bounding box where particles initially appear for this emitter. In addition to the corners (-1, 0.8, -1) ~ (1, 1, 1), the box is further rotated by 45 degrees as seen from the offset rotation.

Velocity

Particles spawn with initial velocity which ranges between the defined values. The velocity is independent in all three directions between X, Y and Z.

Size

Initial size sets the particle’s uniform size when it’s spawned for the first time. A size of 1 will result in a 1 meter by 1 meter billboard or quad when rendered.

Rotation

Initial rotation sets the particle’s angular rotation when facing the camera. Positive values are clockwise rotations. The field only has meaning for camera-facing particles, such as billboards. It has no effect on oriented quads and models.

Color

Material page for further discussion.

3D Orientation

Initial 3D orientation sets the orientation for 3D-aware particles when they first spawn. The editable fields use euclidean rotation which is packed into a quaternion orientation by the engine. The interpolated value is on the shortest path between the two orientations, rather than interpolating each value separately.

Direction

Direction field in the particle properties and sets its initial value. Some shape builders, like the Trail shape or the Direction Aligned Sprite shape use the particle’s direction to properly display it.

Spawn Order

This initializer has no properties. It simply sets an increasing number to each particle spawned from this emitter, starting from 0. The spawn order can be used for sorting or some custom calculations.

Position (Arc)

The arc position initializer positions the particles in an arc (or a straight line if the arc’s height is 0) between two point, the emitter’s position and a target transform component. With random position offset you can cause the particles to deviate a little from their original location on the arc.

Position (parent)

Velocity (parent)

Size (parent)

Color (parent)

Spawn Order (parent)

This initializer requires the parent emitter to also have a Spawn Order initializer. It combines the parent’s spawn number with its own, effectively creating groups of particles among the children. This initializer is required to properly sort and render child ribbon particles.

See also

• Create particles
• Emitters
• Shapes
• Materials
• Spawners
• Updaters