A subtle constraint to optimize is hardware cost. I assume Disney chose to separate the constraints by going with simple hardware shapes, yielding a predictabl

A subtle constraint to optimize is hardware cost. I assume Disney chose to separate the constraints by going with simple hardware shapes, yielding a predictable cost and an easy construction. A good hardware optimizer would also need to engineer assembly, which seems nontrivial. Software costs of optimizing motion for existing hardware are more predictable (~19 minutes of an i7-7700 w/ 32GB, per second of animation). That being said, they acknowledge in their paper that they could optimize certain properties of the robot, like rod size or joint position.