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How do you rotate the hand from a neutral position:

arm in neutral position

to a supinated (palm facing up) position

arm in supinated position[2]

I rotated the forearm bone on the y axis for demonstrative purposes which twists the elbow like a balloon animal

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In actual anatomy, the humerus (upper arm) would naturally rotate about 60-90 degrees, and the remaining 90-120 degrees would be performed at the distal end of the radius/ulna (essentially the wrist). To model this in a blender armature, I would rotate the upper arm bone ~70 degrees, and the forearm bone ~110 degrees.

Of course, this may introduce problems with skinning. You may want to break your upper and lower arms into 2 or 3 sub-bones each, with constraints that keep them from doing anything other than an axial rotation with respect to each other. Then you can weight paint the surrounding mesh in a gradual fashion so the mesh smoothly rotates just like in reality.

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  • $\begingroup$ Thank you Mike! When you mentioned constraints in regard to axial rotation I understood. $\endgroup$ – chris birns Oct 1 '15 at 20:42
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Directions I used based on Mike Metcalf's answer:

Lock editing for all axial rotations except Y axis enter image description here

Rotate forearm 110 degrees

enter image description here

Rotate upper arm 70 degrees

enter image description here

for desired result:

enter image description here

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  • $\begingroup$ I'm not sure there is a need to post this as an answer as it seems to be just confirming that the other answer works. $\endgroup$ – Ray Mairlot Oct 1 '15 at 21:58

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