Joint rotate one way, go the other way...why! HELP

[smeagol]

Hi everyone,

Please help me out with this one! I made one arm and all the rotations work with it, but after I mirrored it to the other side, the shoulder rotates the opposite direction that I am dragging the pivot. What can I do about this???

Thanks for the help

[warpcat]

I don't have Maya in front of me right now buuuut...
When you mirror, you can mirror "behavior" or "orientation". It sounds like you mirrored the orientation, not the behavior.

[smeagol]

Thanks cat,

I guess it must have been the mirror process...I have already binded the character, you think I can change the rotation back with out mirroring again???

Smeag

[warpcat]

Unfortunately no, you'd end up flipping the Joint Orient attributes all over the place, and this will wack out your skin. However.... You can copy the weights:
Save a new version of your scene "B".
In "B", kill the weighting, and rebind it to the exact same joints, but don't wory about making the weights pretty. Save the scene again.
Import scene "A" into scene "B". Select skin A, then add select skin B.
Skin->Edit Smooth Skin->Copy Skin Weights.
Delete objects "A" from the scene. You're good to go.

[twedzel]

It's all about Local rotational axis of your joints. If you select a joint go to component mode and click on the little question mark, you'll see you can select a little XZY handle. You can rotate this freely without it affecting the skin. This little puppy is the visual representation of your joints Local Rotational Axis (LRA). By default your joint LRA are set to XYZ, meaning X is running down the joint... wich means your joint will twist on X. It is very important to have one of these chanels running directly down your joint chain, or you will loose the ability for your joints to effectively twist (Knock your forearm axis out of alignment and you'll see what I mean).

When you mirror joints across, Maya reverses them. Check it out either display local rotational axis for the joints, or go to component mode and hit the little question mark. You'll see they are reversed. This should really be taken care of befor binding, but you can do it after as well by manually rotating them 180 degrees. You can find the numerical values that go along with it under the joints attributes (attribut editor) As you rotate the LRA, check out what happens to the Rotate Axis and Joint Orient values for the joint. You'll figure it out. If you want to correct this befor binding it is easy, just go to > skeleton > Orient Joint and open the option box... choose the direction you desire and click Orient. Simple. Doesn't work after the bind. For future binds keep in mind its very important to have your skeleton joints in the right place nicly cleanly and working befor binding. Same with your UV's etc etc etc.

[zbgump]

First off, this is confusing the hell out of me... this is almost as bad as patch modeling!

I can't seem to figure out how the hell to do this, I exported my branch, reimported, grouped, scaled -x. As you can imagine 2 out of 3 of my rotations are reversed. I've read these posts, all I've been able to is change which 2 axis are reversed! I tried Skeleton>Orient Joint. "Simple" you say? Well, its simple to click the menu item, but it doesn't seem to be getting the results I want! (excuse the sarcasm, much frustration, little sleep) I've tried each one of the possible joint orientaions in that tool. It seems all that does is change which axis has its positive end pointing down the joint. Is that what I want, or do I want all the LRA in both limbs to be pointing in the same general direction in the world space?... ie If in the left arm X is pointing DOWN the joint chain, should X be pointing Up the joint chain in the right arm?

Theres got to be a simple way to solve this. I suppose I could just animate with one side being reversed, but that seems silly.

[zbgump]

OK, I just manaully rotated all the trouble joints 180 in Z, so that the X axis went from pointing down the joint chain to UP the joint chain. Its screwed up in the exact same was as before I rotated the joints. So, rotating the joints 180 has no efffect, nor does playing with the orient joint tool. Anyone have any other ideas, or perhaps I made an error somehow.

Screen: http://users.rcn.com/rmkerr/Stupid_jointshttp://users.rcn.com/rmkerr/Stupid\_joints

(Damit, I hate being stuck like this when all I want to do is work) Pleeeez help.....

edi: OK, I noticed something that might help someone help me. When i import the joint chain, I group it to itself. So, it has a clean channel box. The joint in the skeleton that it gets grouped to has a relatively clean channel box, just some slight transform, which I think is usual with joints. Now when I group the group node to the skeleton, the group takes on some craze attributes in the channel box: 133 rotate in x, -1 scale in Z roate 90 in Y etc...while the joint, in the branch, immediately below this sloppy group node is relatively clean. WTF?

[zbgump]

I've posted this at buzz and cgtalk...sorry to be rendundant but I need to get my work done.

How do you all go about mirroring joints in your skeletons. I tried a technique from a gnomon video which I thought would work. I exported my arm which had set drivens in the hand. I imported the arm, grouped it to itself, then parented the group node to the hierarchy. The set driven keys seemed to still work, but 2 of the 3 the rotations were reversed. Why, I don't know. No matter how I tweaked the axis, all I could accomplish was changing which axis were screwed and which one wasn't. My first question is, can I just go with this and animate my character with one side being sort of opposite? I think I can work with it, but I don't want to go through all the trouble of skinning only to have this bite me in the ass later on down the road.

Now here was my other idea. I thougt I would just go ahead mirror the branch with the mirror joint tool, and then just redo all the set driven again on the other hand manually. It wasn't that big of a deal I thought. But, for some reason, Maya seems incabable of trully "mirroring" this branch! True, the joints look the same and are in the same relative position, but the local rotation axis aren't trully reflected! WTF! I can't even do this manually if I want to! I have to mirror the joints, and then go in and eyebal all my LRA to get them to be a mirror copy of the other arm. Is this normal? How the hell do people work like this? What is the point of the mirror joint tool if you have to do most of the rough work manually anyway?