Collision

The collision system in Unity refers to the detection of a physical interaction between objects in the level.

Houdini Engine for Unity can generate collision from many types and sources:

complex collisions
convex collisions
simple collisions

To create collision, assign your geometry to the Group SOP node and use the proper attribute prefix as the group name.

Groups ¶

Some special group names have naming schemes which specify generation behavior when marshalling data from Houdini to Unity.

Primitives that belong to collision groups will be separately created as Mesh Collider components and added to the output GameObject. The rendered_collision_geo groups will have MeshRenderer and MeshFilter components as well.

Collision ¶

Colliders can be automatically added to generated meshes by using keywords in group names for geometry. These group names are:

Mesh Collision ¶

Group Name	Description
`collision_geo`	Adds a non-convex, non-rendered mesh collider
`rendered_collision_geo`	Adds a non-convex, rendered mesh collider

Simple Collision ¶

Known as Unity Primitive Collision

Group Name	Description
`collision_geo_simple_box`	Adds a simple box collider (ignores geo in group). It will be an axis-aligned box with dimensions encapsulating all the vertices in the geo group
`collision_geo_simple_sphere`	Adds a simple sphere collider (ignores geo in group). It will be an axis-aligned sphere with dimensions encapsulating all the vertices in the geo group
`collision_geo_simple_capsule`	Adds a simple capsule collider (ignores geo in group). It will be an axis-aligned capsule with dimensions encapsulating all the vertices in the geo group
`rendered_collision_geo_simple_box`	Adds a simple box collider with geometry created as mesh. It will be an axis-aligned box with dimensions encapsulating all the vertices in the geo group
`rendered_collision_geo_simple_sphere`	Adds a simple sphere collider with geometry created as mesh. It will be an axis-aligned sphere with dimensions encapsulating all the vertices in the geo group
`rendered_collision_geo_simple_capsule`	Adds a simple capsule collider with geometry created as mesh. It will be an axis-aligned capsule with dimensions encapsulating all the vertices in the geo group

Convex Collision ¶

Group Name	Description
`convex_collision_geo`	Adds a convex non-rendered mesh collider
`rendered_convex_collision_geo`	Adds a convex, rendered mesh collider

Triggers collision ¶

Add trigger in the names above in order to convert the collider into a trigger (i.e. enable the Is Trigger toggle). Note that for Mesh Colliders, they must be convex. The geometry will be generated as a separated mesh from other geometry, and set as the mesh in the MeshCollider component.

convex_collision_geo_trigger
rendered_convex_collision_geo_trigger
collision_geo_simple_trigger_box
collision_geo_simple_trigger_sphere
collision_geo_simple_trigger_capsule
rendered_collision_geo_simple_trigger_box
rendered_collision_geo_simple_trigger_sphere
rendered_collision_geo_simple_trigger_capsule

Level of Detail ¶

lod

Prefix used for defining mesh LOD level (e.g. lod0, lod1)