How Do You Determine How To Orient Joints?

[onemoretime]

I feel silly given my last topic. But, all the books I have leave a big gap here as far where the axes should point. Is there some tutorial or example that has all the joints oriented correctly already? I think I sort of get it but I see lots of conflicting or incomplete things online.

[gmask]

I can't think of many instances where you wouldn't want an axis pointing down the joint. So if we are talking arms here then the X is pointing down the joint and Z is pointing towards forward. At least this is what Maya does by default. Otherwise if they are not aligned this the joint will rotate in an odd way which usually isn't desireable. Just open a front view in Maya and make a skeleton and observe how the axis are created. I think this used to be a bigger problem in older versions.

[onemoretime]

Thanks, that was helpful. In addition, I learned you want to have one axis point to the direction of bending to make it easier to rig. It seems odd there's not too much outright talk of how they should be oriented but I guess once you learn to make a rig it is sort of obvious.

[daikath]

hmm this was informative, all I knew a axes had to point towards the next bone.

[gmask]

QUOTE(Daikath @ 05/21/09, 09:36 AM) [snapback]308138[/snapback]
hmm this was informative, all I knew a axes had to point towards the next bone.

not neccesarily and they don't have to being aligned with the world space but imo it is logical to do so.. there will be times when they won't such as if you want your symmetric character rig to mirror motion by flipping one of the local rotation axis on the joints.. but there are other ways to do that

[uiron]

you want your three gimbal axes represent a somewhat "forward, side, up" alignment. it's just really up for the rigger to decide. for limbs this _most_of_the_time_ (but not always) represents next bone as "forward" (X), and bending axis as "side" or "up". "not always", would be, example, orienting the wrist bone (the one that when rotated, rotates palm area) - i usually pick X as looking to index finger, Y stays in paralel with the imaginary plane of the palm and Z represents the "normal" of the palm plane. just the usual "forward, side, up" pattern.