heya!
Yeah, so the upperarm twists and thigh twists work the same way, where they try to keep the ‘attach’ point to the body, from stretching and skewing. So on the upperarm, it keeps the shoulder in place, and on the thigh, it keeps the crotch from twisting. So it’s best to think of weighting those as top to bottom, where top is twists, and bottom is parent.
The calf and lowerarm twists however, are reverse of that. They take a percentage of the child joint and spread that up, rather than countering. So they work bottom to top, where the bottom of the part is twists and the top is the parent bone.
Hope that makes sense!
examples:
https://www.dropbox.com/s/em31449d5x4bvpq/thighTwists.gif?
https://www.dropbox.com/s/168tyog9srd7z5a/calfTwists.gif?
