PhysicsShape.ContactFilter.groupIndex

Description

Collision groups allow a certain group of objects to never collide (negative) or always collide (positive). A group index of zero has no effect. A non-zero group always overrides the category/contacts masks. The rules for two shapes coming into contact are:

• If either shape has a group of zero then the group is ignored and the category/contacts masks are used.
• If both shapes have a non-zero but different group then the category/contacts masks are used.
• If both shapes have an identical and positive group then they will always produce a contact.
• If both shapes have an identical and negative group then they will never produce a contact.