Hello,

I was changing the geometry obj loaded in houdini geometry node for the groom, the topology is the same, but shape is different.

The guides generated in the guide groom mode appear to follow this changed shape without issue but the hair generation node then shows big bald spots with no hairs in parts of the groom. Is there a workflow that allows us to change geometry once guides have been created within the guide groom node that will propagate to the hair generation node as expected?

Best,

Erin

I should note that I am currently using 19.0.720 for rendering with vray.

It is usually easier to provide support if there is some file to look at. This file does not have to be your "real" project file, but just illustrate the case. This is just a small hint.

Thanks SWEST,

The file is on our secure network, it's commercial work for tv, so there isn't a way for me to share it. I'm learning on the job in the absence of any training and support so it's fun but a bit frustrating when things start going wrong.

It certainly took a while to figure out why every tutorial on hair on youtube was different than what I was seeing with the new tools in 19. The results are fantastic though!

Do SideFX staff answer here or is it user peer support in the community?

Don't know if it works, but did you try using a "blendshape" instead of replacing the geometry ? Since the topology is the same...

Thanks toonafish,

I tried, and I receive an error: "Warning: Skin input doesn't have a rest attribute.
Error: Couldn't find skinprimuv attribute.. " Any ideas? I'm going to look that up in the meantime, see if I can find anything on it.

Here's a basic scene with a shape that deforms a hairy torus, looks like it could work if you have a a similar setup:
https://www.dropbox.com/s/pzbwspzmd9um60n/HairShapeDeform_01.hiplc?dl=0 [www.dropbox.com]

Thank you toonafish, I'll give it a try. I appreciate you taking the time to help!

Funny, now I'm running into similar issues.

I have to adjust the head geometry after I edited a hair groom, but when I replace the head geo the hair groom does not move with the shape of the new geometry. It sticks to the old groom topology, essentially the same problem as what is mentioned at the start of this thread.

But this time it's an animated alembic file so I can't use a blendshape.

So to revive this topic, I assume this is a bug ? Because if you can't even adjust the underlying geometry of a hair groom it would almost completely beat the idea of a procedural groom.

Heck it would be even less flexible then grooming in almost any other 3D app.

Any ideas, besides redoing the groom ?

Thanks

Houdini 19.5.493

Just in case someone else runs into this issue, or I forget.

Looks like Houdini doesn't allow you to simply replace the original Alembic file and reload the scene. That would be too easy, and will screw up your hair groom.

But so far it looks like you can circumvent this bug by keeping the original geometry as the "static" geo for the groom, and then use a shape with the adjusted geometry for the animated skin.

Basically the same as the scene in the example before, but then with an alembic for a blendshape .

But I'll report, maybe it will be fixed some sunny day.

if you are talking about Guide Groom, its most likely not a bug
https://www.sidefx.com/forum/topic/88387/ [www.sidefx.com]

if your topo is the same, you can probably use Guide Deform and then new Guide Groom to continue

Hey thanks.

Looks like there the "Guide Deform" used in the default shelf hair groom setup on the obj level. And there's another "Guide Deform" to be connected somehow in the Guide Groom.

I used the default shelf setup, but suspect you're talking about the second flavor guide deform because the obj level guide deform only has a single output.

Does that need a different kind of setup, other then the default shelf one ?

I can't seem to find any info on how to use the Guide Groom inside the groom SOP.

Or am I misunderstanding what you mean ?