topic Re: Problems with pinning cloth in Bifrost Forum

Problems with pinning cloth

BrianHanke — Mon, 21 Jun 2021 17:49:09 GMT

Hi all, I'm having trouble getting Bifrost to behave consistently in this test. I want the cloth to fall down and stick to the animated figure's shoulders. Was easy enough to accomplish in nCloth using a stickiness map and Houdini has vellum attach to geo. I can't figure out what Bifrost is doing here though. As you can see, it appears the cloth is sticking to something well above the surface of the model. The end of the clip shows the constraint mask I painted. Any tips about what I can do to make this work better? Thanks!

Re: Problems with pinning cloth

Christoph_Schaedl — Wed, 23 Jun 2021 05:35:22 GMT

Have you seen Jasons video about Cloth?

https://youtu.be/xGGFrQvKXwM

Re: Problems with pinning cloth

BrianHanke — Thu, 24 Jun 2021 21:30:12 GMT

Thanks. Interesting video, but I don't think it addresses my problem. It feels like what's happening is like when you have a very low res VDB collider in Houdini. I tried messing with all the settings that seemed relevant, but the collisions with the animated figure are always out of whack. I don't have the same problem with simple test geo. Not sure what the difference is...

Re: Problems with pinning cloth

bugsdabunny — Sat, 26 Jun 2021 05:26:08 GMT

Can you post the scene for debugging?

Re: Problems with pinning cloth

syracoj — Tue, 06 Jul 2021 18:18:13 GMT

Hey Brian,

attached is a scene file of pretty much an MPM cloth setup from scratch (see scene file in ZIP).

The only thing I changed was modeling a different poncho shape assuring that the neck opening of the poncho fit tighter around the subject's neck. My Vertex color paint application was more conservative and went all around the neck and was smoothed out (see the attached image in the zip). The cloth sits up and off the model because all the Detail Size and Detail Size Scale are at their defaults. You could refine it by setting the Detail Size Scale on the solver_settings node to a lower value like .4 or .3 (this will be a slower calculation).

I did assure that the constraint was checked to use the color property and I had to increase the constraint nodes strength from 1 to 3.

As we see in the attached video (in the zip as well) the response is improved but could be taken further because again, most of the MPM settings are at their defaults. You could try lowering the inherit velocity on the collider but lowering this too much may cause the arms to pop through the poncho.

I think better modeling of the poncho will be key and a more sparingly use of color weight to control the constraint will help as well. Let us know if this helps.

You could also post the ABC file on here (if you can share it that is) and others may be able to give further guidance. There are a host of other settings that could be adjusted to give a better response.

Re: Problems with pinning cloth

BrianHanke — Tue, 06 Jul 2021 20:58:16 GMT

Thanks so much, John! I went through your comments, made a few small tweaks and the behavior of the sim is excellent now. I think the "falling into place" part makes things overly complicated, so I'm going to try with a fitted garment next.

Thanks again!