PDA

View Full Version : Softbody Dynamics



mccabejc
10-22-2007, 08:02 AM
I'm coming back to LW after a couple of years absence, so I'm just starting to re-learn the ropes. As I recall, the last time I used LW (LW7.5 I think), Motion Designer was still a bit messy, to say the least, and one of the major limitations I faced was the inability to assign softbody dynamics to one of a character's surfaces, rather than the whole thing.

I'm wondering if the LW 9 incarnation of Softbody has improved. For example, if I want to animate floppy jowls, jiggling belly, or any other jiggling part of a high poly character, how do you do it now? I read that ClothFX seems to be the preferred method for dealing with softbodies like this, as opposed to the built-in SoftFX function.

Thanks.

Greenlaw
10-22-2007, 11:49 AM
We've had great success using ClothFx for this sort of thing. In many cases, the key is to use ClothFX with a low poly cage object, and then applying this object as a deformer to your hi poly object using Metalink. The nice thing is that with Metalink the low poly object only needs to vaguely resemble your hi poly object, (in other words, no worries about breaking point order like with the old Metamation method,) and calculations are VERY fast this way. Frequently we can get away with using simple sub-divided boxes or poly-chains as Metalink deformers. Naturally, the shape of the cage depends on the effect your going after. Using this technique, we were getting near realtime calculations for cloth and hair in the Fable 2 E3 trailer a couple of years ago. (I think you can still see this trailer at the R&H website.)

There are other tricks you can use with ClothFX and Metalink, such as using plug-ins or scripts to generate cages with 'stretch constraints' coming from the cage. The constraints are used to help hold the shape of the object so you don't have to rely too much on ClothFX doing this for you. It's a cheat, but what a great cheat! We use the technique often for clothing and body jiggle. There was a handy plug-in that did this called FastCloth, which is no longer available, but somebody wrote a similarly useful script a while back. I haven't used this new script but it's supposed to work the same way. I believe you can find more info here:

http://www.newtek.com/forums/showthread.php?t=24699

Then there's Syflex for LightWave, which is fast and very realistic. In some situations you can just hit play and tweak your settings on the fly. We used it Syflex for LightWave on a recent project, and we were very pleased with the results and how quickly it got us there.

The downside is that the plug-in is expensive, but if you qualify you can get a student license for a very reasonable price. I think the student license is about $220.

Having said that, we still use ClothFX for a lot of things. If you know a few tricks, it's just too useful.

You should also check out this hair tutorial at SpinQuad for using ClothFX with Metalink, polychains, and a morph target. We've used this fast calculating technique on several jobs and it works great. (For example, we used it for the long wind-blown hair hair of the female magician in the above-mentioned Fable 2 trailer.) More info can be found here:

http://www.spinquad.com/forums/showthread.php?t=11582&highlight=long+hair+test

Hope this info is interesting.

DRG

mccabejc
10-23-2007, 06:49 AM
Thanks, good info. I was playing around with Metalink and it's pretty slick.

I guess the thing I have the most difficulty figuring out is how to take a complex character which is controlled by bones, and is comprised of many surfaces (skin, lips, eyes, etc.) and apply softbody to only one of the surfaces (jowls or breasts, for example).

It would be great of LW could do this directly (ie, select ClothFX by surface, not by object), but since it can't, it sounds like the only way is to:

1. Make the softbody part a different object (in a different layer of the main character object),
2. Assign one of the softbody obj's surfaces as "Fixed"
3. Parent that softbody object to the main object,
4. Somehow make the "Fixed" surface affected by the bones in the main object

It gets confusing real quick. Especially if you then want to apply ClothFX clothes.

Any hints would be greatly appreciated.

Thanks.

Dodgy
10-23-2007, 10:18 AM
Are you using SoftFX or ClothFX? Soft FX can be limited using weight maps, or you can indeed use fix in ClothFX.

'Fixed' areas are affected by other deformations such as bones anyway. I usually animate a lower poly proxy character and have the higher rez one parented to that, with metalink on. Then you can simulate fast on the low rez one too.

mccabejc
10-23-2007, 03:12 PM
I'm using ClothFX, based on what I've read here. Plus the fact that I can't, for the life of me, figure out the SoftFX settings. Makes no sense whatsoever...

Anyway, I guess my challenge is trying to apply different FX on different parts of the same character. Softbody on the belly, collision with clothing on the legs, etc. It sure would make things infinitely easier if LW had softbody by surface.....

Dodgy
10-23-2007, 03:34 PM
Well you can apply multiple effects to the same character, using weight maps or selection sets to control where the effects are, or their strength. Fixed points on an effect which is on top of another, will still deform according to the fx below, they just won't be affected by the fx their defined by.