Download

Ray tracing breaks hair shader

Unfortunately ray tracing seems to break the hair shader. Anyone got an idea how to fix this? Just tried 4.23 and it’s still broken.

1 Like

No, it is a solid mesh hair, with no transparency (like say a Daz character has.)
Here it is in Octane Render

Same result with Sparrow. It has nothing to do with GI (not even activated in my test) or the geo of the hair. It’s definitely a shader issue.

1 Like

Hmmm…
because looks what happens with a Daz character with RayTracing GI ON and then OFF.
Clearly there is a difference caused by Raytracing GI’s shadows, or shadow-attempt on the hair:

(see attached Photos, noting RayTracing Global Illumination Enabled “ON” and then “OFF”, and then line where hair meets skin of face)

But you know what, Frankie V said that shader from Paragon, which you are now last citing as having same issue, looks fine. And this got me thinking, there is now the 4.23 Preview, which does have RayTracing updates, and also says under “Rendering Updates”:

  • **Dynamic Shadow Bias Improvements. **We have added a new Slope bias parameter which, in addition to the existing constant Bias, help to resolve some issues with some manual adjustments without creating shadow acne.

Perhaps this may help us? Because it is that shadowing that is being affected/darkened. I have not tried yet.

Hey, potentially good news to report. I tried 4.23 Preview and the blotchy black issue on imported Daz hair is no longer present!
So, we might be in luck now with the scene that had been tested with UE4 Mike and Paragon Sparrow if tried in 4.23.

In my image here, you can see top line of hair there is no dark blotch. I moved scene angle around and changed lighting , and the blotchiness is never present even if RayTraced GI is enabled/ON.

NOTE - you will see something else funny, the mirror’s reflection has black hair. This is because UE4’s raytraced reflections (ie a mirror) do not properly handle Translucent materials yet.
This Daz hair is run as Translucent with Opacity maps to mask parts of the mesh (as is case with basically all Daz-type hair).
You can also see lashes and eyes are dark too, this is because they also are Translucent (lashes like hair, and cornea-eye reflection has opacity driven translucency).

Anyway, 4.23 holds the key maybe!