Hair black squiggles/lines/intersections in Iray Render, solution inside.
Falco
Posts: 241
I found a ton of posts with complaints about black squiggles showing up in iray renders without a lot of good solutions. I found that this typically occurs when the haircap intersects with the model. I just wanted to post a solution I found since I didn't see it posted.
The reason this was happening in my renders was that my subd level on my character wasn't set to be the same number on the hair object. Having these be different numbers was the main cause of the issue for me, as it caused the tesselation on the haircap and the figure to no longer match, and the intersections are what cause the squiggles.
One additional wrinkle was that I was using a very expensive short hair asset that was about 250k triangles for the base model. My character was set to subd 3 for rendering, and there's no way I could increase the subd on the hair to match that as my gpu would run out of memory. My solution was to duplicate the hair object, and then in the geometry editor I deleted everything except for the haircap faces on that duplicate, and deleted only the haircap on the other. Now I had 2 separate objects for the hair and haircap, and I could set the haircap to subd 3 without any issues. This fixed the black squiggles and also kept my scene cheap enough to fit on the gpu.
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Comments
Very interesting. Thanks for letting me know about that. I've always wondered where the squggles come from.
As a follow up, in case anyone else stumbles here with the same problem, I had the issue and it was caused by "invisible collision gloves," which didn't have a sub-d setting, so had to be removed/hidden. There may be a solution that works, but I didn't need them in the scene, so I just dropped them completely.
Or you could scale the hair up by 0.5%
I got this to work with 0.15% increase (tried lower, as low as 0.05 and 0.1 but those didnt work for me)
Yeah, I always solved this issue by increasing the size of the hair cap. I never considered the SubD as a cause/solution. I'm gonna try this out next time I have that issue. Thanks!