Problem with orient constraints in Maya 5

[kevvyb]

I have a rigged character with a piece of cloth (not Maya Cloth, just geometry) hanging from his wrist. I made this work in Maya 4.5 by adding a locator beneath him and constraining a joint in the cloth to the locator (except the Y rotation so the cloth turned with the character). This meant that however he moves his arm the cloth hangs down. I made the cloth a softbody so that it has momentum and moves nicely. However, this doesn't work in Maya 5.0. It keeps flipping (180 degrees maybe?). If I lock all 3 axis the problem disappears but the effect doesn't work. It's like an IK flip but I can't figure out what's changed in Maya 5.0 so I can try to correct this.

Any help will be gratefully received.

[nonquad]

Are you saying it's the same file and no longer working, or just similar technique?

If it's just similar technique, then the devil is probably in the details. For example I imagine you could run into some problems depending on which order of rotations you use. It's only safe to cut the input on rotateY if the other two axes are independent from it; ie the object is order xzy or zxy. Otherwise you'd get flipping exactly like you described.

If the orient constraint doesn't work out for you, you could always use a point and aim constraint to get the effect you described.

Here's how:

Two locators, B parented to A. Move B down a few units so it 'hangs' under A. Point constrain A to the wrist, so now "B" is hanging under the wrist. B is going to be your control handle. (although if you are like me, you'll want to "B" to be something more aesthetically pleasing than a locator)

Anyway.
Have your wristcloth aim towards B, with the elbow specified as an up vector. Now the cloth stays in plane with the arm, while "hanging" down, as requested. One nice effect of doing it by aim constraint, is that the aim target provides a great handle by which to sway the cloth around. It also gives you some control over the solution when the arm goes vertical; since you control the axis yourself, you can ensure that it is never allowed to be colinear with the arm, which would cause flipping.

[kevvyb]

It's exactly the same file. They've changed the way constraints work to add some features, but the documentation seems a little vague (probably just me though).

What I've ended up doing is to add an IK spline to the strip of fabric, make the curve a soft body with springs and add gravity. I discounted this before as being too complex for a cartoon character. (Also, I forgot to add springs last time I tried it and the cloth fell through the floor!)

This is probably a better solution although I'm going to try what you've suggested. Thanks.

[nonquad]

All depends on how much detail you want to add.
If you're doing a soft spline, I'd say have the goal object constrained with aim constraints as described before. That way you can have your soft secondary motion, with some tweaking control as well.

[kevvyb]

That's a good idea. Thanks for the input.