Maya Muscle provides one more utility for collision/sliding, which is the Muscle KeepOut node. This node lets you drive the translate/rotate of a transform node, such as a group, so that the node can “slide” or collide with any Muscle object (such as a capsule, muscle, or bone).

This gives you the power of Maya Muscle’s Sliding algorithm, allowing for sliding or collision-type effects, but with transform objects. Using Muscle KeepOut nodes, you can create a number of interesting rigging tricks or constraints.

For example, you can create a ground plane, make it a Muscle Object, rig an animation control to slide against the plane, and get ground locking effects. Or, parent a special flatten joint to an arm and have it collide with a capsule or Muscle Object in the chest as the arm lowers, keeping the arm always outside the chest. KeepOut nodes give you sliding effects paired with custom rigging possibilities using joints/transforms and constraints.

For objects like muscles or clothing, you can create a rib-cage capsule or muscle, then have a joint that “keeps-out” from that node, so that even if the animator poses the arm down, the skin joint collides and does not penetrate.