This skeleton has twist bones for arms, forearms and thighs. I’m trying to work out a solution that will isolate the rotation of the twist bone, but I’m coming up short. I’m focusing on the thighs right now, hoping that the solution can be applied to the arm and forearm.
Looking at both Rigify and Pitchipoy, I’ve noticed that they have different setups for where the thigh rotates: one does it a the hips (current state), the other at the shin (which I’d like to to do, if possible).
The last thing I did that sort of worked was to parent the ThighTwist bone to the Thigh control bone and place a Damped Track on the ThighBend targeting Thigh Twist. The problem there is that rotating Thigh control too much on the Y axis will cause ThighBend to spin rapidly.
I only changed the .L thigh DEF bones, but it should give you the idea.
I made sure DEF-ThighBend.L was exactly half the length of Thigh_FK.L and aligned with it. Then it copies that location and scale, and does a stretch to Shin_FK.L. Then DEF-ThighTwist.L just copies the rotation of Thigh_FK.L
EDIT: I don’t know what happened there. I did it a couple times to make sure I was doing what I thought, but the DEF-ThighTwist.L somehow got a driver on the copy rotation constraint??? Delete that driver and set the influence to 1 and it works as expected.
I’m also trying to figure out how to do the thigh twist bone and have the same problem. Your pasteall has disappeared and I was hoping to look at it too. Do you think you could post it again. Thanks!
It’s been a while, and I don’t remember exactly what I was thinking then or what I put on pasteall.
The way I do it now has four layers of bone groupings…
Control bones, mechanism bones(MCH)(layer 30), tweak bones(TWK)(layer 22) and deform bones(DEF)(layer 31).
They follow each other in that order.
The mechanism bones switch between the FK and IK control bones.(most of the IK control bones are hidden and also have the MCH prefix because they aren’t user controlable. (Layer 13))
The tweak bones are parented to their respective mch bones, then the deform bones each do a copy transforms of the tweak bone at it’s head then a stretch to the tweak bone at it tail.
OK, enough of that BS. Let’s get down to the question. The Shoulder/Hip tweak bone does a damped track then stretch to the Elbow/Knee tweak respectively. And the tweak midway on the arm/thigh does a 50% copy rotation of the mechanism bone.
What this does is allow the rotation bone at the hip/shoulder to point at the knee/elbow without twisting and the twist bone adds the twist along the length.
I’ll try to attach a blend file you can pick apart… (I’m still new to this forum update so we’ll see how that goes.)
EDIT: The upload didn’t go perfectly. I didn’t save the open version that had the correct items selected and the properties panel open to the armature context. Also, you probably need to click the “reload trusted” button in the top header bar to get the rig to operate properly.
