Hi everyone,
I posted these last week on CGTalk and thought some here might be interested. I have made a pair of free Maya Python plugins, a hip constraint and a shoulder constraint. Each of these is designed to govern the rotation of the first twist joint in a twist structure for each respective part of the body.
Because they are both Python nodes, you can see the source code, but just briefly, each of these is basically a custom aim constraint whose up-vector programmatically rotates through the limb’s range of motion. The main advantages over a pose-based system (irrespective of the fact that I think the result will be the same in most all cases unless someone really wants some kind of funky deformation) is that each constraint only uses a single slerp driven by one or two dot products. This makes it substantially fewer cycles and also reduces setup time since the poses do not need to be defined by the user.
Each is available on my website in a ZIP file. Each ZIP file contains the plugin, an example file, a setup script to add the constraint to an existing structure, and a setup script to build the whole twist structure on the limb. Please let me know if you have any problems while using them so I can improve them as necessary.
Shoulder Constraint
Hip Constraint
Thanks!