In this lesson you learned some fundamental concepts with respect to rigid body dynamics.

• There are differences between active and passive rigid bodies.

  When a rigid body is passive, active rigid bodies can collide with it but will not move it. You can control its movement by setting keys.

  When a rigid body is active, you control its movement using dynamic forces, specifically fields and collisions. You can change the active and passive state of the rigid body to achieve various effects. For example, you can roll a ball off a table using keys (passive rigid body) then cause the ball to fall using gravity (active rigid body).

• A hinge constraint can be used between an active rigid body and a position in the scene view.

  You can also create a hinge constraint between a passive rigid body and a position in the scene view, two rigid bodies, and an active and passive rigid body.

  Other types of constraints include pin, nail, spring and barrier constraints. For additional information on the types of constraints and their usage, please refer to the Maya Help.