Fix rigid body problems
As you work with rigid bodies and rigid body constraints, you might see warning or error messages in response to your actions. Common messages and solutions follow.
Errors when you create a rigid body
Error: Attempting to create a rigid body from the shape or hierarchy ‘object’ which already contains a rigid body.
This message means you tried to create a rigid body from an object or object group that already has a rigid body created for it. You can create only one rigid body for an object or object group.
Delete the rigid body of the object and recreate it.
Warning: The surface of rigid body ’rigidBody1’ may be reversed. Reversing the surface may avoid interpenetration errors.
This message occurs if the rigid body solver calculates that the surface of a rigid body is facing the wrong way. Only one side of an rigid body’s surface can collide with another rigid body’s surface—the side with normals pointing outward.
Reverse the NURBS surface or polygonal object’s normals.
Error: The rigid body cannot be created because the selected shape contains polygons which do not have unique vertices. Use the polygon tools to determine bad polygons.
This message means you tried to create a rigid body from an object that has at least one polygon with two or more coincident vertices. For example, the object might contain a triangle with four vertices.
Use polygonal modeling tools to fix the polygon.
Warning: Selected item "rigidBody1" is not deformable.
This message occurs when you create a rigid body from an object that has a deformer, skin, or flexor applied to it. Because rigid bodies cannot deform, Maya applies the rigid body to the original, undeformed object that is hidden when you apply the deformer to it. The resulting rigid body might seem to collide at the wrong time.
For example, suppose you animate an active rigid body sphere bulging from a lattice deformation. The bulging area penetrates rather than collides with a nearby passive rigid body cube. You won’t see a collision until the original, undeformed part of the sphere moves against the cube.
Warning when you set the center of mass
Warning: The center of mass is locked. To edit the center of mass, set the ’lock center of mass’ attribute to false.
If you turn on an object’s Lock Center of Mass attribute and try to change the Center of Mass, the above message occurs.
If you want to change the Center of Mass, select the rigid body, display the Attribute Editor, and turn off Lock Center of Mass.
Error when rigid bodies fail to collide
Warning: Rigid Body interpenetration occurred between ’rigidBody1’ and ’rigidBody2’.
Only one side of an rigid body’s surface can collide with another rigid body’s surface—the side with normals pointing outward. Interpenetration occurs when two or more rigid bodies pass through each other. This typically occurs when one body passes through the wrong side of another.
Though it’s valid and often desirable for one passive rigid body to penetrate another, it’s invalid for an active rigid body to penetrate another rigid body, whether passive or active.
If you’re unsure which objects interpenetrate, look in the Outliner. Maya selects and highlights the objects after the warning message occurs.
Warning when you cache rigid bodies
Warning: The rigid body is currently cached. Changing an attribute will have no affect until the cache is manually deleted via the Solvers->SceneCaching->Delete menu.
This message occurs if you’ve selected Solvers > Memory Caching > Enable for a rigid body, then you change attributes on the rigid body that affect the rigid body’s translation or rotation. Because the rigid body is cached, it gets the translation and rotation information for the rigid body from the cache. You won’t see any effect on the rigid body until you delete the cache.
Select the rigid body and select Solvers > Memory Caching > Delete.
Error when a solver computes rigid body dynamics
Error: Error detected in rigid solver computation. Solution may be invalid.
An invalid internal computation occurred, possibly because of conflicting rigid body constraint forces. This message typically occurs with a message warning of an incorrectly positioned constraint.
If rigid body constraints are forcing a rigid body to interpenetrate with another rigid body, reposition the constraints or rigid bodies.
Warning when you delete rigid body connections
Warning: Cannot disconnect: ’rigidBody1.choice’ from ’rigidBody_tx.selector’. To force the disconnection, set the ’Allow Disconnection’ attribute in the attribute editor.
In the dependency graph, a rigid body node controls the transform node of the rigid body object with connections through several choice nodes. The choice nodes let you key passive rigid body Translate and Rotate attributes so you can switch from keys to dynamic influences and vice versa.
Maya usually lets you break the connections to a transform node’s Translate and Rotate attributes, for example, by selecting the attribute in the Channel Box then selecting Channels > Break Connections. For rigid body transform nodes, breaking such connections would cause the rigid body to lose control of the transform node. Because of this, Maya prevents you from breaking the connections in the usual way.
To remove the keyframe connection to the rigid body, select Soft/Rigid Bodies > Break Rigid Body Connections. This removes any connection to the rigid body not specifically used by the rigid body, for instance, connections to keyframes.
To break the connections from the rigid body to the choice nodes or rigid body solver, you must first select the rigid body or rigid body solver, display the Attribute Editor, and turn on Allow Disconnection. Breaking these connections might cause unexpected results.