maya cycles eg,
parent constrain A to B, parent constrain B to A
breaks Maya.
Instead Constrain A to B, but turn off B's constrain to A
When you want A to control, turn off A's to B and turn on B's to A.
Use condition nodes and pair blends. Pair blends are generated when you set a key in such a cycle. Lock the pairblend nodes.
Its ok to delete keyframes AFTER you lock them.
Within condition node you need to use RGB to set states and values for certain nodes. In the case of A and B, you want to set the parent Constraint node to either 0 for normal, or 2 for blocked.
you also need to set the weight to 0 or 1. The final value is the pairblend weight.
The downside/requirement of such a setup is you must keyframe every shape involved. eg you want to use A to move left to right, and B to go up and down, on keying you MUST key both shapes otherwise they override each other.
