Dynamic skirt only using joints

[justahackn]

Hi...

try tweaking the rest curves of the hairsystem for more control - I've setup joints with the restcurve bound to them in the past - works very well 'cause it forces the hairsystem to catch up to the new rest pose, allowing you to keyframe your dynamics layer.

good luck.




Hey everyone, I have something that works but very hard to control due to the nature of what I have to work with.

What I am trying to do is set up to dynamically drive a skirt on a female character to react to her movements. The tricky part is I only have skinned bound joints that have to move skirt around and even worse, I only have a root joint in her leg and the end joint which controls the ends of the skirt around her legs.

What I have tried so far is using both the hair and softbody solvers by using a spline IK and making the curve dynamic so the ik and joint follow it. This works but again, its very hard to control even when trying to put collision objects in to stop it from running through her body.

Any tips or ideas that I may be over looking?

Thanks for your help and feedback,
Scott

[Remi]

This may be a stupid question. Did you make your collision objects larger than what they need to be? That might help some of the pass-through. I didn't completely understand the joint setup, perhaps a screengrab of just that area if you can't show the whole thing? Making the spline IK dynamic would probably be the best way if it has to be joint driven. Are there controls for each joint chain in the skirt? If not, you might try setting those up as well just so if you need to, you can hand-key them as well if they still pass-through. Again, sorry if this doesn't help. I'm by no means a dynamics wiz.

[zhenyang]

Hi, what I've done for a previous job was set up 2 joint chains with spline IK, one hair driven and another with animation controls, which is skin bound. The hair driven joints would drive the control joints. So animators would try to find a good-enough settings and do a sim, cache it, then hand-key extra tweaks.

[scottiedoo]

Thanks guys. Yeah the rest curves do help. But I found a better solution which is starting to give me better control.

Originally the skirt was modeled already around her waiste and the joints positioned close to the body which didn't give me much room to control. So I have the modeler put her skirt flat like an inner tube with the joints out and then have them fall into place which is a lot nicer than before.

If there are some parts pentrating, then some hand keying will be added later on those joints in another package so the job is to simply apply animation, bake the simulation and kick it back out.

unfortuately I only have a root and end joint, so there is no middle 3rd joint which would be extremely nice but not possible.

Feels like I am working with a hammer to screw in a bolt. But somehow its going to work :-)

Any more suggestions let me know, and once I figure out a good solution I will post it for future reference if anyone else is in a similar situation.

Thanks for your help, I have tried several of your ideas so far so keep them coming if you got them.

[yenvalmar]

you could set the skirt up with a real cloth sym, then have the joints follow its motion, for example by using the rivet script to attatch them. then have you other in game skirt driven by those joints, the simulated skirt would jus be used to create the animation.

that way you dont have to half ass the simulation itself.

i have done a fair amount of fake cloth with the hair system driving skeleton rigs and it always winds up needing to be manually fixed at the end. i havent tried the other way but next time this comes up its a thought i had after my last project doing what you are trying to do :)

i also have a bit of experience with "real" cloth and the new ncloth system is a huge improvement- if you were scared off by the old ccloth youll be impressed. what i have not done is hook up the real cloth system to a game rig yet, you can let me know how it goes :)

you will also want to rig manual over rides on all your joints so its easy to fix when things penetrate. the nature of the situation is such that its literally impossible to avoid all penetrations by rigging the joints directly, becuase a lot of the cloth goes between the joints. by using a real cloth sim to drive the joints it should mitigate that problem by correctly calculating the collisions with the geometry. i have a feeling it still may not be 100% perfect as the joint chain and binding wont give identical deformation to the sim- but the motion will be handled properly for sure and thats a lot of the battle.

[scottiedoo]

Yeah, I thought about doing a real cloth sim and then parenting the joints to clusters of the cloth and trying to closely as possible weight the skinned skirt to match, but my experience in cloth is none. I am working in 8.5, I know that 2008 has improved a lot of its cloth stuff which is great, but I ran out of time and couldn't spend time to try this method out.

So what I did was just reposition some of the bones to give me better collision and remodeled the skirt so it dropped down and settled rather than being in a settled position at the start.

yeah I couldn't get rid of all the collisions as some of the animation is way to large of movement to keep it from not going though, but the big deal is atleast is I'm getting good motion without having it freak out or get stuck anywhere, so some hand keying will be used later to fix the spots that couldn't be solved with the collision.

There was just a lot of toying around with different values like how many CV's were in the curve mattered a lot on how hair moved, I found the lower curve detail worked better but barely having any or no stiffness still gave me flexable movement, but having a little "start curve attraction" help it from doing whatever it wanted.

So thanks everyone for their help, I wish I had more time to try better and newer methods, but time was not on my side this time. But for how important it is to the game, this is better than they expected for what I had to work with. So mission successful I guess

thanks for you help guys, I greatly appreciate it.
Scott

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