Particle Initializers

This page lists and describes all particle initializers.

Box Position Initializer

Initializes a particle’s position to a random point within a box shape.

PositionOffset, Size: These values define the size and position of the box, relative to the origin of the particle system. With a position offset of (0, 0, 0), the box will be centered around the system’s origin.

ScaleXParam, ScaleYParam, ScaleZParam: Optional names of effect parameters. This allows to scale the volume in which particles spawn.

Note: Scaling the volume will change particle density. To compensate, the particle system will automatically spawn more or fewer particles. Thus you can author an effect as a 1x1x0 meter sized patch and then let the user decide how large a patch she needs by exposing these parameters. If your 1x1x0 patch requires roughly 100 particles at all times, then scaling it to a 10x5x0 patch will require 5000 particles.

Cylinder Position Initializer

Initializes a particle’s position to a random point either within a cylinder or on its surface. A cylinder of height 0 initializes the position to a random point on a circle or its circumference.

PositionOffset, Radius, Height: These values define the size and position of the cylinder, relative to the origin of the particle system. With a position offset of (0, 0, 0), the cylinder will be centered around the system’s origin. A height of 0 turns the cylinder into a circle.

OnSurface: If enabled, particles will only spawn on the surface of the cylinder, not inside it. This also excludes the caps. For a cylinder of height 0 that means the particles will spawn on the circumference of a circle.

SetVelocity, Speed: If enabled, the initializer will additionally set the particle’s starting velocity. The velocity is always outward from the cylinder’s center line.

ScaleRadiusParam, ScaleHeightParam:

Optional names of effect parameters. This allows to scale the volume in which particles spawn.

Note: Scaling the volume will change particle density. See the box position initializer for details.

Sphere Position Initializer

Initializes a particle’s position to a random point within a sphere shape.

PositionOffset, Radius: These values define the size and position of the sphere, relative to the origin of the particle system. With a position offset of (0, 0, 0), the sphere will be centered around the system’s origin.

OnSurface: If enabled, particles will only spawn on the surface of the sphere, not inside it.

SetVelocity, Speed: If enabled, the initializer will additionally set the particle’s starting velocity. The velocity is always outward from the sphere’s center.

ScaleRadiusParam:

Optional name of an effect parameter. This allows to scale the volume in which particles spawn.

Note: Scaling the volume will change particle density. See the box position initializer for details.

Random Color Initializer

Initializes a particle’s color to a random color.

Gradient: If specified, the random color will be picked from the given color gradient.

Color1, Color2: A random interpolated color between the two given colors is used. So if one color is white and the other is black, particles will get a random grey value as their color. If a gradient is set as well, the two colors are combined.

Random Size Initializer

Initializes a particle’s size to a random value.

Size: The base size for the particles to start with. To initialize all particles to have a fixed size, set the variance to zero.

SizeCurve: If specified, the curve is sampled at a random location and the normalized value (always between 0 and 1) is used to scale the randomly chosen base size. The shape of the curve has no meaning for this use case, it only provides a way to affect the distribution of the random sizes. For example, you could have a curve that sets exactly half of all particles to exactly a tenth of the base size. If you want exactly the same distribution as the curve has, you should set the variance of the base size to zero.

Rotation Speed Initializer

Initializes a particle’s rotation and rotation speed to a random value.

RandomStartAngle: If enabled, the particle will start out with a random rotation. For particles with a distinct texture or shape, this can make the effect look significantly more natural.

DegreesPerSecond: If set to a non-zero value, particles will rotate with a constant speed. Each particle gets its own random speed assigned. With a low variance all particles will rotate similarly fast, with a high variance you will see some particles rotate very fast and some very slowly. Half of the particles rotate clockwise, the other half counter-clockwise.

Velocity Cone Initializer

Initializes a particle’s velocity to a random up vector.

Angle: The maximum opening angle of the upside down cone. With a small opening angle, particles will fly straight up. With a wide opening angle, particles will fly in all directions.

Speed: The initial speed for the particles.

See Also