Hi Guys it's urgent

I’ve posted it on CG talk, but no response. Then I heard that this is dedicated site for blender. So please take a lokk about the problem…

I’m in rigging stage of my first character for my short film. Rigging is almost done. Yesterday I just wanted to final check my first rig for animation. But…a silly things happend. After that I checked all the rig like Mancandy, billy(kajimba), and rigs from Big Buck Bunny. And all the rigs contain the same problem. I surprised, then I do just a quick setup but yes the same problem.

Now the problem is in hand setup. I used B-bone for forearm twist. And when I rotate the wrist Y more than 180( assuming that make the armature in top viewport, so rotation Y will be responsible for twisting the forearm), forearm breaks(flip) from the elbow. Then I just do old spliting joint setup( place 4 joints for forearm) then assign copy rotation with the wrist, and changed the value of influance accordingly. But again the same thing happend. Whats the problem?

Well after searching the rotation of each joint I saw the wrist is going inverse. I mean, suppose I’m rotating it in negative value but when it goes in -180 it converted +180. And same thing is like +180 converts in -180. Then I just make an armature and go into pose mode. Try the rotation, belive me the same thing again.

Conclusion is, when I rotate an object or armature in object mode rotation goes properly but when I switch to pose mode rotation only took 180 to -180, even it’s for a single armature too.

What is the problem. any idea???

I assume you’re talkng FK setup?

If I grab Mancandy’s forearm, then push [R][Y][Y] to rotate it along Y as you have described, you’re right - the bicep does pop at a certain point. Is this what you mean? It looks to me more of a vertice weight issue than a bone one, possibly avoided by not twisting the arm beyond what it would normally do.

Am I missing something?

no man, this is not any weighting issue, just rotate an armature in pose mode(create and rotate), then watch the value, you can see when it goes -180 it starts from +180…

Yep, that’s normal. Blender handles the rotations of armatures in a different way from the RotXYZ you are expecting. Instead it used QuatXYZW… I personally don’t like it because I think it makes animation adjustments in IPO editor (curve editor) difficult.

See more here: http://blenderartists.org/forum/showthread.php?t=158912

Hmm…interesting

FYI, the reason for this is to avoid Gimbel lock. When You have you do standard rotations using sin,cosine, you can run into places that the rotation freezes up mathematically. Quaternions are the solution to the problem. They work different because they are different. The Quaternion does not suffer from such rotation locks, and is a more affective algorithm.