[diffeomorphic] some hairs look like plastic in cycles

bigoskar00

so I have this issue with diffeomorphic where some of the hairs that I export looks like they are made from plastic. This only happens with some hairs, while some look perfectly fine off the box and others look fine in eevee for some reason some look weird in cycles and only in cycles

here are some examples:

the hair is https://www.daz3d.com/alyssa-ponytail-hair-for-genesis-8-females?srsltid=AfmBOorllVCJVUcgEAn377Nk6OHSMRtskKLNoroaZkQIysz0kr4z5sS5

before someone asks I know about light paths and how some hairs need the light paths to be cranked up, this are the numbers that I used for this preview

and as a comparison here is the exact same hair with nothing changed in eevee

as you see it looks more natural like actual hair

this happens with a few of the hairs that I use but not with all of them, some look perfectly fine in cycles right out of the box with no issues, here are some examples

https://www.daz3d.com/hs-smooth-bob-hair-for-genesis-9-8-and-81-females?srsltid=AfmBOoqBxoX8wrPR8r16_skLlON1-EzRI6d63WaFbMamleXyiVEUPfId

https://www.daz3d.com/catrina-hair-for-genesis-9?srsltid=AfmBOoo4JKaFtE7dMbGkYQKngYKRKFJeXp_LXuSAqd0SV-ehxGtD7q3A

https://www.daz3d.com/fe-refined-short-hair-for-genesis-8-and-genesis-9?srsltid=AfmBOorUr7ASQ0wLtNuFOynAQ7EZpkX_Jr2N3yAdbKYSRelIWOUSAgo6

those three hairs looks fine in cycles and eevee, I have no issues with those

Padone

What is your light source ? It seems there's strong lights from all sides, while reflections need a main light on a relatively dim environment to show off better. Did you try the same light in daz studio what you get.

hardwire666

Make sure it's using the normal map. I imported the asset myself and the Normal map makes a massive difference Diffeo doesnt import the normal map in either FBX compatable, or Extended for that asset. 

Padone

Yes, I can confirm. Alyssa is using the BDL hair shader, which is intended for strands, while Alyssa is geometry ribbons not strands. The BDL shader is approximated in blender, so it doesn't generally look the same as iray, especially if we use the principled option as eevee can't render any hair shader in blender, so it is converted to principled. With the BSDF option the conversion is better, as it is converted to a hair shader in blender, which only works with cycles.

The bump map is not imported as it doesn't make sense for hair shaders in blender.

However, there's an option in the global settings for hair materials. The "smart" option will ignore the BDL shader if the hair is not strands, and use a uber conversion instead. This way the hair is converted as if it was a uber shader, and the bump map is imported. Still it will be different than iray.

Another option with this kind of hairs, is to convert to uber in daz studio before exporting, just applying the uber shader. As again BDL is intended for strands. In this case the conversion will be the same as iray.