Control which objects collide with which

[sntran]

trafficstars

For example, some entity can go through wall, etc

[sntran]

Crafty has the Gravity component with a .gravity(comp) to specify which component whose entity should stop the current entity from falling.

In Box2D, a static object will stop the entity. You can specify which object that the current object can bypass that collision. Quite a contrast.

[sntran]

In Box2D, there is categoryBits and maskBits that would define it. Just need to figure out a good way to implement.