Bone Replacement

This is just a simple rigging note that I've found useful in Maya.

When rigging in Maya, you may occasionally want to replace some bones in the skeleton, this can be annoying after you've already done some weight painting to the skin. The skin deformer knows which bone a weight is assigned to, but the actual weights reference a bone by name only. So we just need a new deformer. You can swap any of the bones in the skin deformer pretty easily by following this procedure:

• duplicate original_bones, creating new_bones
• remove the original_bones from the skeletal hierarchy
• rename new_bones to match original_bones

At this point, our model is still skinned to the original_bones. We need a temp model skinned to new_bones to ensure we preserve our weights.

• duplicate model, creating model_temp
• make skin on model_temp using the skeleton (which now includes new_bones)
• copy weights from model to model_temp

Now we have 2 meshes, skinned to both skeletal instances with the same weights. Though model_temp is correct, we usually don't want to trash our original model, so re-add the skin and copy the weights back.

• detach skin from model
• make skin on model using the skeleton
• copy weights from model_temp to model
• delete model_temp.

It's a fairly simple process, but very handy.