I have a static body A, and a dynamic body B, and a dynamic body C. A is filtered to not collide with anything, B and C collide with each other. I wish to create a joint between B and A. When I create a joint (ex. revolute), B no longer collides with C - C passes through it as if it does not exist. What am I doing wrong? How can adding a joint prevent a body from colliding with another body it used to? EDIT: I want to join B with A, and have B collide with C, but not A collide with C. In realistic terms, I'm trying to create a revolute joint between a wheel (B) and a wall (A), and have a box (C) hit the wheel and the wheel would then rotate. EDIT: I create a the simplest revolute joint I can with these parameters (C++): b2RevoluteJointDef def; def.Initialize(A, B, B -> GetWorldCenter()); world -> CreateJoint(&def);