I'm working on rigging a character for an upcoming short film and have a puzzle to bring to the table regarding hip/thigh rigging. While rolling the thigh bone on my character (and pretty much every library character), I observe a disconcerting tendency of the pelvis to simply collapse. To remedy this, I'm exploring the use of a chain of "fan" bones to distribute the roll of the thigh along a series of thigh cross-sections, giving the hips a much-needed break. I've currently tested my design with a simple tube model and the results look promising. It basically works like this:
A chain of roller bones is constrained to the thigh and the thigh geometry is assigned to them. The rollers are constrained to Orient Like the thigh, but the roll is achieved by separate Roll Like constraints which gradually add up to the full roll of the thigh by the time they reach the knee.
Spiffy! I was pretty proud of myself...until I brought this back to my actual character model and realized that legs are not perfect tubes!
The conundrum I'm facing now is that I want to apply this principle to a thigh bone that is not straight up and down and to leg cross sections that don't perfectly line up, vertically. Between proper bone hierarchies and constraint options, I'm currently stuck. I've attached the project file with my two concept tests. Any pointers on how to create a chain of roller bones that move with a thigh but maintain their own unique pivot points along the leg so that each leg cross-section rotates, more or less, around its center?