hair raytrace shadow popping

[JackDwarf]

Hi!

I have hair raytraced shadow popping/flickering issue on my render.
It’s a static camera. There is no Lod on hairs, no binding, no simulation, no animation.

I tried to follow this below thread, but only the deep shadow cast is stable. But I would like to get soft shadows, so I need stable raytraced shadow.

The shadow of the HairGroom asset is flickering.

I’m using the HairGroom feature. I’ve attached to the skeletal mesh and the Groom shadows appear to flicker in and out. It seems to be happening from a certain point in the local Y coordinate, and is stable at the top. Changing the scale of the actor seems to have reduced the flicker, but I could be mistaken. Also, the reason I thought it was a shadow is because the flickering can be reduced by reducing the value of Hair Shadow Density. How can I get rid of the flickering here? Please help…

Do you have any idea to fix it please?

I’m currently using UE 5.1, hardware raytrace shadows enabled, with only one distant light with 4 rt samples per pixel (I tried 32 samples, it’s still flickering).

Thanks!!!

[JackDwarf]

Hi!

I found a solution to fix the flickering/popping shadows from raytraced hair shadows.
I just enabled the groom shapes attr “Use Attach Parent Bound”.

On my character there are many hair shapes. Their bounding boxes provoke this instability I guess.

Cheers!