UE 4.25 - SSS texture alters Opacity (Quixel Foliage) Tweet

[PeteUmptone]

Hello,

If I use any SSS Unreal Material and provide it with a Texture sampler in the SSS output, it seems like the SSS Texture somehow influences the Opacity mask output as well, no matter what kind of map i provide. Switching to a single Constant Float3 value instead in the SSS part of the material immediately fixes the Alpha issue.

[youtube]https://youtu.be/8A4e40cbJjI[/youtube]
(https://youtu.be/8A4e40cbJjI)
I'm using the default (fairly simple) quixel foliage material as an example.


Thanks in advance!

[ChrisHekman]

I have the same material im not getting the same results. Could you test if this still happens in the latest (0.36) version?

[PeteUmptone]

Thanks for the Quick Answer Chris,
I'm checking it out!

[PeteUmptone]

After installing 0.36 and having a little bit of digging into it:

For me, the default Quixel Foliage Material still has the same alpha issues, although recreating the material from scratch with the same textures is working..


(Fig. 1: Left - Quixel , Right - Custom Material)



(Fig. 2: Left-Quixel Material, Right - Custom Material)

The material setup is kind of exactly the same, checked all the other checkboxes, not sure what am I missing. What's even more strange is that it seems like a texture related issue in the Quixel-to-Octane material, changing e.g. the SSS Tex (Which is in this case pretty dark) to the albedo (which is way brighter) makes the Quixel material visible in Octane:


Chaging the SSS texture to Albedo makes it visible (which is strange)

I've Also tried to adjust the SSS texture inside Unreal to brighten it up, but it had no effect in the Octane material:



Applying the over-bright SSS map in the Quixel default map results in a 0 alpha Octane material.

The Albedo and Translucent maps are identically RGB, from jpg source, with BC7 compression, they have exactly the same parameters but their colors.

I've used the up-to-date Quixel Bridge, imported a random foliage asset into an empty Ue 4.25.1 project with Octane 0.36. I hope I could explain it clearly.


Also tried to Create a new Master Material asset in 4.25 and copied the Quixel node graph into it, same result. I'm 100% sure Octane samples the SSS texture for the Opacity mask. If I start to crank up Opacity intensity (which is after the Opacity texture!), the alpha starts to come back in, but with the luminosity value of the SSS map:



Strangely high values are bringing alpha, but with not the Opacity Mask Tex as sampler source



And Again, Not using SSS Map in the Material immediately fixes the material (uses the correct Texture for Opacity Mask):


Thanks for your Help Chris in advance!
Peter

[ChrisHekman]

Thanks for the thorough documentation, I think I found the issue. Ill check if i can fix it.

[PeteUmptone]

Thanks for the thorough documentation, I think I found the issue. Ill check if i can fix it.

Thanks Chris!