A Hinge constraint constrains rigid bodies along a specified axis by a hinge. You can use a Hinge constraint to create effects such as a door on a hinge, a link connecting train cars, or a pendulum of a clock. You can create a hinge constraint between:

• one active or passive rigid body and a position in the workspace.
• two active rigid bodies.
• an active and passive rigid body.

The Hinge constraint is able to react to forces. Its axis rotates when torque is applied, which gives it a realistic look when your hinge is flying through the air or bouncing against other rigid bodies.

To create a Hinge constraint

1. Select the one or two rigid bodies you want to constrain.
2. Select Soft/Rigid Bodies > Create Hinge Constraint > to display the options window.
3. For the Constraint Type, select Hinge.
4. If you are constraining two rigid bodies and want them to penetrate each other rather than collide upon contact, turn on Interpenetrate.

   If you turn on Interpenetrate, playback of rigid body animation is faster.

5. Turn on Set Initial Position and enter X, Y, and Z values for the position.

   If you don’t turn on Set Initial Position when you constrain a single rigid body to a position, the Hinge constraint is created at the rigid body’s center of mass.

   If you don’t turn on Set Initial Position when you constrain a pair of rigid bodies, the constraint is created at the midpoint between their centers of mass.

   Though a passive rigid body has a center of mass that Maya uses for default positioning of Hinge constraints, Maya doesn’t use the center of mass in dynamic calculations of passive rigid bodies.

   Tip

   After you create the constraint, you can use the Move and Rotate tools to change its position and orientation conveniently in the workspace.

6. To set the initial orientation of the constraint axis, enter X, Y, and Z values in degrees for the Initial Orientation.

   By default, the hinge constraint lies parallel to the world space Z-axis.

7. Click Create in the Constraint Options window.

   To alter the constraint after creation, see Edit constraints.

   
   Tip

   You can make a directional hinge, which always maintains the direction of its axis. This is how the original hinge constraint worked prior to Maya 4.5. After you create the hinge constraint, set the Constraint type to directionalHinge in the Attribute Editor or Channel Box.