XGen Interactive Groom Hair Flipping when rendering on Farm

[Anonymous]

Hey everyone,

I'm having an issue with XGen's interactive Groom splines, hopefully someone can help!

I got several shots delivered for rendering in Arnold with different characters all who have hair/fur/eyebrows created with Xgen Interactive Grooming. The characters are animated but the fur is not dynamic, it only follows the geometry.

Now when I render on my pc different frames, everything is fine, but as soon as i send the rendering to our render farm, the hair starts popping / flipping / wiggling however you would like to call it. This doesn't occur in every characters, those without any noise in the hair don't seem to have that problem. Also during a shot the amount of wiggling may change from going totally crazy to almost non existent and this doesn't seem to be related to how much a character moves.

I've tried several things, turning Modifiers on and off and in one of the characters it definitly comes from the noise in the clumping modifier. Other characters don't have noise in the clumping, but they do have noise modifiers, so i guess the noise is the problem. For the noise modifiers there's an option to bake the noise, but I think that doesn't quite work, because nothing happens when i click the button, and it wouldn't fix my problem with the characters with noise in the clumping modifier anyway, since they don't have such a button.

I cached my XGen descriptions to alembics, this works just fine on small scenes with very little hair in it, but isn't doable at all for bigger scenes. For some characters this takes hours to export while others simply crash. And I have scenes with so many characters with so many hairs, that this workflow is just not effective.

In other posts I read about this being caused by several clumping layers, but this can't be the cause in my scene, because there's only one clumping layer.

A bake modifier would by great, but this doesn't seem to exist for interactive grooming.

I also read about the $pref variable which should be used in expressions with noise, but I don't think any expressions were used here, just the noise sliders.

So yeah.. is there something obvious I'm missing?

It has to do something with the render blades computing the noise differently... If you have another idea than caching the descriptions, rendering only locally or rendering without noise in the groom, let me know!

Thanks in advance.

[sean.heasley]

Hi @Anonymous and welcome to the community!

This is a bit tough to test since I don't have access to a render farm. Its also unusual that caching isn't helping as this usually solves issues similar to this 

What is your evaluation mode set to, DG or Parallel? Changing this may help.

Let me know if anything changes!

[Anonymous]

Hey Sean!

Thanks for the reply!

Haven't checked my evaluation mode yet, will definitly try that on monday.

I might have been a bit confusing on the caching part. Caching the hair definitly helps, when i cache my hair it isn't flipping anymore, so it is a solution; but the problem here is that I can't cache all my scenes, because some are so heavy they just simply crash while caching (or they are taking forever to cache).

[Anonymous]

I just tested changing the evaluation mode, sadly it didn't help.

[sean.heasley]

Hi @Anonymous

Hmm ok.

I understand a few of your scenes are extremely heavy but if you try a batch render of a few frames and/or a cleaner scene on your local machine and not the farm does the same issue occur?

[sean.heasley]

Hi @Anonymous

Just wanted to check in to see how things were going. Are you still having this issue?

If your issue is resolved, please click Accept as Solution on the posts that helped you so others in the community can find them easily.

[Anonymous]

Hey Sean,

I guess we could make the caching work somehow, I was just hoping we don't have to. I thought it might be just the click of a button I am missing...

Could you maybe explain the "Bake Noise Data" in the Bake Options of the Noise Modifier to me? Because nothing ever happens when I switch the Mode to Baked or click the button and this seems like exactly the thing I need for at least half my characters.

[sean.heasley]

Hi @Anonymous

Sure thing, we actually have an article on that you can find here!

From that article:

For xgmModifierNoise nodes, clicking Bake Noise Data saves the baked the CV offset data to the Maya scene file.

So when you use this bake option, you don't notice any difference in your render times?

[Anonymous]

Hey there,

having exacly the same issue and I was wondering if you found a way to make it work !

thank you !

[Anonymous]

Hey there @sean.heasley,

having exacly the same issue and I was wondering if you found a way to make it work !

thank you !

[sean.heasley]

Hi @Anonymous

Did you have a chance to try the step I posted above?