Iray - hideous black marks on character skin

andya_b341b7c5f5

Can someone please suggest what might be the cause of the Iray horror show on this poor girl's forehead?  I don't believe they can be shadows: there's nothing to cast shadows like that in the scene.  Lighting is an HDRI supplemented with a distant light from her left.  Looks like she's had an unfortunate encounter with a vindictive tattoo artist.

mjc1016

Which version of Studio?

Which main model, character and hair?

 

Chohole

Is it possible that it is part of the hair, a hair cap without a transmap applied?

mjc1016

Chohole said:

Is it possible that it is part of the hair, a hair cap without a transmap applied?

That's one possible cause.  Another, but similar cause is that the transmap for the cap is being read wrong...Iray needs black and white maps for opacity cutout...and one that isn't properly greyscale or has an embedded color profile/incorrect gama won't read correctly.

A third is a variant of the bug that affected mainly eyelashes, but sometimes hair, in 4.8, where if things were shifted from 0,0,0 center wild things went on...

andya_b341b7c5f5

Thanks both for the suggestions.  I'm using 4.8, and it must be a position related bug because if I move the figure to somewhere closer to 'ground zero', though still some way off world center, she looks much happier and of course the same transmaps are in use.  Even if this bug is completely fixed in all its variants by 4.9, for a number of reasons I have no intention of migrating to 4.9 until I am forced to do so kicking and screaming.  Pity there is no 'backporting' of fixes for important bugs like this.

 

TesseractSpace

Yeah, I remember reading something about being a certain distance from center causing issues. Dunno if it's fixed in 4.9 but I think it was