About Rigid Bodies
A rigid body is made up of one or more parts that do not move relative to each other. By default, rigid bodies in Design Animation are created following the Mechanism Dynamics rules, parts with a constraint between them are placed in a single rigid body. For more information on rigid bodies, search the Help Center.
Keep the following points in mind when creating rigid body definitions:
• Rigid body definitions created in Design Animation will not transfer to Mechanism Dynamics.
• Depending on the constraints used to create your assembly, you may want to redefine the model using One part per body or Edit.
• If a rigid body definition has been edited and saved in a subassembly, you cannot edit the rigid body in a higher level assembly. You must edit the rigid body in the subassembly, then save it.
• If a subassembly rigid body configuration is not saved, a default rigid body definition is automatically created. The default definition can then be edited.
When you click 
Rigid Body Definition, the Animation Rigid Bodies dialog box opens:
Rigid Body Definition, the Animation Rigid Bodies dialog box opens:• Click New or Edit to open the Rigid Body Definition dialog box and create a new rigid body or edit an existing one. Any parts added to a rigid body are removed from the rigid bodies that previously contained them. All parts automatically belong to the ground body if they were assembled using user defined constraints.
• Click Remove to remove a selected rigid body. Other parts in that rigid body are moved to the ground body.
• Click One part per body to create rigid bodies using the one part per body rule. All connections are retained.
 | Use one part per body with caution when defining large assemblies because each part in the assembly becomes an individual rigid body. You will also have to redefine the ground body. |
• Click Default bodies to revert to the original rigid body definitions. This option causes the assembly to automatically regenerate, and then reassign parts to rigid bodies. Any rigid body definitions already created are ignored.
| | Best practice is to use default rigid bodies when defining rigid bodies in your assembly. If you do not, regeneration may fail or parts may be placed in different locations when you open or regenerate the assembly in another mode. |