Transform constraints with Cloth object !#@!

[thomaslandvik]

Here's what I have:
- A polygon object made into a cloth object.
- A skeleton with cloth collision objects parented to it.
- A transform constraint on a series of vertices on the cloth object. This constraint is parented to a joint.

This is the general idea:
The cloth is driven by the collision objects which are moved by the skeleton. The constraint nails a part of the cloth to the skeleton so it is in effect rigid.

THIS IS THE PROBLEM:
The transform constraint seems to lag after it's parent (the animated joint)!! The amount it lags seems to be directly affected by the "Time step Size" of the cloth solver, but it always lags, kind of like a spring would. Is this a known problem with Cloth constraints? I have tried it with all the other cloth constraints and the problem is still there. It seems ridiculous to have to increase the time step size to unworkable proportions just to reduce (but never get rid of) this annoying affect.

Any suggestions?!?!?

[mestela]

Nope, it should work like you expect. The transform constraints aren't set as soft are they? If so, you'll need to set the stiffness really really high for it to not lag (I was using values like 1000, 2000).

If they're hard constraints, check you're only turning on the constraints once the cloth is in place. Cloth transform constraints will maintain their offset from the target as soon as they're turned on, so if the cloth has to settle first, key the transform constraints to 'on' maybe 5 frames after the settling is done.

(edit) One other thing, see if you can construct your setup using panels rather than a poly object converted to cloth. Cloth gets unstable unless you use that irregular tesselation cloth likes. (/edit)

-matt

[thomaslandvik]

Thanks for the info. The constraint was definitely not soft, so maybe it was the "settling" issue.

When you say that "cloth gets unstable", in what way do you mean? Are you talking unpredictable in its behaviour, or does it cause Maya to crash? If it's just the tesselation which differs (surely it's the same algorithm) then is it just that the folds and bends are uglier and less "cloth-like"?

[mestela]

Yes and yes.

Generally its more of the 'doesn't look good', but when cloth verts start to get really wacky (collapsing in on itself, making giant sliver faces etc), cloth normally crashes soon after.