CollisionFilter

@Immutable

data class CollisionFilter(val categoryBits: Int = 1, val maskBits: Int = 65535, val groupIndex: Int = 0)

Collision filtering parameters used during broad-phase and contact filtering.

This DTO follows the common (Box2D-like) collision filtering model:

categoryBits defines which category this body belongs to (bitmask).
maskBits defines which categories this body can collide with (bitmask).
groupIndex provides an explicit override: bodies in the same non-zero group can be forced to always collide or never collide, regardless of category/mask.

Typical rules (engine-dependent but widely adopted):

If groupIndex != 0 for both bodies and the values are equal:
positive value => always collide
negative value => never collide
Otherwise collision is allowed when: (a.maskBits & b.categoryBits) != 0 && (b.maskBits & a.categoryBits) != 0

Note: although fields are Int, most physics backends treat masks as 16-bit values; only the lower bits may be used.

Constructors

constructor(categoryBits: Int = 1, maskBits: Int = 65535, groupIndex: Int = 0)

Bitmask representing the category of this body (usually a single bit).

Optional override group. 0 means "no override".

Bitmask representing categories this body is allowed to collide with.