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User Guide (Version 1.14)

Collision Attribute

Parameters in this attribute control the particle's physical setup.

CPU Collision Attribute Parameters

Parameter Function Description
Physics Type Specifies how the particle interacts physically.
  • None – No collisions or other physics. This setting is used by default.

  • SimpleCollision – Collides the particle with the static environment using simple physics. This is the simplest mode.

  • SimplePhysics (Geometry particles) – Creates a particle in the physics system and collides using a spherical particle model. Use Surface Type to set the bounciness.

  • RigidBody (Geometry particles) – Creates a particle in the physics system and collides using the full collision mesh of the assigned geometry. This is the most expensive mode. Use Surface Type to set the bounciness.

Collide Terrain Includes terrain in particle collisions.

Default value: false

Collide Static Objects Includes non-terrain, static objects in particle collisions. This is expensive.

Default value: false

Collide Dynamic Objects Includes non-terrain, dynamic objects in particle collisions. This is expensive.

Default value: false

On Collide Upon impact with the static environment, the particle dies.
  • Die – The particle dies upon colliding with an object.

  • Bounce – If you enable Collide Terrain, Collide Static Objects, or Collide Dynamic Objects, the particle bounces off the respective type. If none of these are enabled, the selected particle ignores the object that it collides with and passes through. This is useful with Spawn IndirectionParent Collide.

  • Stop – The particle stops when it collides with an object.

Default value: Die

Max Collision Events Limits the number of collisions that the particle can have in its physics simulation. This affects only particles that have Physics Type set to Rigid Body.

Valid values: 0 – 255

Default value: 0

Bounciness Controls the elasticity for collision response. This affects only particles that have Physics Type set to Simple Collision. You can override this feature by setting Surface Type. You can also use a special value of –1 to have the particle die on first collision.

Valid values: any

Default value: 0

Collision Fraction Determines the fraction of emitted particles that perform collisions.

Valid values: 0 – 1

Default value: 1

Collision Cutoff Distance Specifies the maximum distance from the camera at which collisions are performed. A value of 0 means infinite.

Valid values: 0+

Default value: 0

Surface Type Selects from a variety of surface material types for the collision behavior. If set, Surface Type overrides Bounciness and Dynamic Friction.

Default value: none

Dynamic Friction The coefficient of dynamic friction. If set, Surface Type overrides Dynamic Friction. This affects only particles that have Physics Type set to Simple Collision.

Valid values: 0+

Default value: 1

Thickness Controls the fraction of the particle's visible radius to use for the physical radius. This affects particles that have Physics Type set to Simple Physics and geometry particles that have Physics Type set to Simple Collision.

Valid values: 0+

Default value: 1

Density Controls the density of particle in kg/m^3. An example of a physically correct value is Water = 1000. This affects only particles that have Physics Type set to Simple Physics or Rigid Body.

Valid values: 0+

Default value: 1000

GPU Collision Attribute Parameters

Parameter Function Description
Depth Collision Specifies how the particle interacts physically.
  • None – No collisions or other physics. This setting is used by default.

  • Frame Buffer – Collides with the screen space depth buffer.

  • Cubemap – Collides with a depth cubemap buffer that is generated around the emitter.

Cubemap Far Plane Sets the far plane distance for cubemap depth buffer generation.

Default value: 20

Die on Collide Upon impact with the static environment, the particle dies.
  • Die – The particle dies upon colliding with an object.

  • Bounce – The particle bounces off the object that it collides with.

  • Stop – The particle stops when it collides with an object.

Default value: Die

Bounciness Controls the elasticity for collision response. This affects only particles that have Physics Type set to Simple Collision. You can override this feature by setting Surface Type. You can also use a special value of –1 to have the particle die on first collision.

Valid values: any

Default value: 0

Thickness Controls the fraction of the particle's visible radius to use for the physical radius. This affects particles that have Physics Type set to Simple Physics.

Valid values: 0+

Default value: 1