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.
![[box-position-init.gif]]
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.
![[cylinder-position-init.gif]]
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.
![[sphere-position-init.gif]]
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-color-init.gif]]
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.
![[random-size-init.gif]]
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.
![[rotation-speed-init.gif]]
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.
![[velocity-cone-init.gif]]