A mask that defines which categories this physics body belongs to.
- iOS 7.0+
- macOS 10.9+
- tvOS 9.0+
- watchOS 3.0+
Every physics body in a scene can be assigned to up to 32 different categories, each corresponding to a bit in the bit mask. You define the mask values used in your game. In conjunction with the
contact properties, you define which physics bodies interact with each other and when your game is notified of these interactions.
The default value is
0x (all bits set).