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It's not displacement, I get the same thing in clay mode or with a blank white mat. I've also tried it with Iray and Octane standalone, standalone has the black stuff the same as OcDS, Iray is fine and without issue. I've even updated my drivers.

It looks like an opacity map issue to me. If you send me a ORBX file demonstrating the problem, I can take a closer look.

Paul

I'm also having a problem with this hair, in fact I think it affects all recent OOT hair with hair blending, but this one is by far the worst, I just have to make parts of them not visible and the black stuff starts to show up. The hair(s) also seem to render extremely slowly, this image only rendered at 0.99Ms/sec using PT.
Rey Epsilon is 0.000001 (auto setting off), changing it doesn't seem to do anything much.

I have discussed this issue with Otoy, and their response is

The reason why the hair in this scene still is somehow rendering black in some places is because we allow a ray to only trace through 64 transparent surfaces before we give up and make the sample black. If we wouldn't limit the number of traces through transparent surfaces, ray-tracing sooner or later will get caught in an infinite loop where it doesn't progress, due to numerical issues. This will basically block the kernel and eventually crash the graphics driver.

So in summary - it is because there are too many transparent layers on top of each other. This also explains the very slow render time.

Paul

Ok, thanks for all the help, guess I'll just have to be very careful with OOT hair from now on.

Thank you Paul for your help.
So, I need to modify geometry to render properly.

Thanks

Ok, thanks for all the help, guess I'll just have to be very careful with OOT hair from now on.

This is the correct answer...

His hair might be of a very high quality, but it definitely comes at a price. The structure is way to complex with several layers of alpha-mapped materials overlaying each other.
Now add to that our shader and you have transmission and subsurface scattering going on as well.

At this point he might just as well switch to geometry based instead of alpha-map-based hair figures...

Hello,

I apologize for resurrecting this thread, but I did not see a direct resolution. Going into DAZ, I realized that this hair has multiple "settings" which makes it, in my opinion, unnecessarily complicated. Regardless, going into the geometry tool, selecting the geometry for the 'bun' (if you want to see the ponytail), selecting the surface "backunder", hiding it, then deleting it resulted in fixing the back part of the hair.

Unfortunately, the front part is still an issue. You, again, have 2 silly options for "bangs". A sideswept look or a straight bang. Unfortunately, with this one, it gets more complicated. Even though I chose the "sideswept" version of the bang, the original, straight bang still casts a shadow:



Please pardon my godawful quality screenshot. Even though I've "moved the polygons from her face", Octane still thinks the straight bang is there, and is thus creating a shadow.

I do not know how to resolve this, and welcome any assistance.

3dx

Yeah I've come to experience that issue just as well...it needs time to resolve.
Something around the 1000-3000 S/P mark should get rid of the shadow.

I know this is out of left field, but any thoughts by anyone interested in this topic as to what Iray is doing that would make it work, vs Octane needing to 'tip-toe' around these hair meshes?
Like, I know that there are theoretically too many opacity maps stacked, but why would Iray be able to handle and render the hair, but not Octane?

I had a similar issue with Genital models where the model joins to hip with an opacity cut out. Sometimes that part won't show properly and instead you get to see through my guys body at the hip. I found that I had to reload his torso texture and rebuild scene. Just wondering if the hair blending uses an opacity cut out to blend .. might be something to look into.

I use OOT hair models too and I haven't had this exact issue. I'm pretty new an Octane so I'd assume my render settings are mostly default at present. I use Genesis 3 and 8, male and female models with OOT a lot .. but I don't use hair blending .. because I've never gotten that to work at all.

So, check if there's an opacity cut out ruining your day.