IN PROGRESS: Question about roughness maps and unreal engine 4.

kurylo3d

I am makign art for unreal engine 4 so i set quixel to that. I noticed that the roughness map generated is not greyscale on one of the things. It has color on some parts. To my understanding roughness is a greyscale value.

I know unreal has metallic, roughness, and spec slots. So i guess my question is what should be going in the spec slot and also why the non grey scale roughness texture exported out of quixel?

loggie24

Roughness/gloss is grayscale. Certain metals have a colored specular map though so that's most likely what you are looking at.

kurylo3d

I guess im a little confused. When i plug the map into the spec channel inside unreal... it kinda just darkens the reflection to hte point that its barely visible. Rather hten adding any sort of color to it. And the thing that came out of quixel is still called roughness map. How do i plug this stuff up to look correct in unreal engine 4. I am using the unreal engine 4 presets so im confused.

loggie24

hmm, i'm not familiar with Unreal so better wait for Eric or some other guys that know it better.

Synaesthesia

You shouldn't be connecting the roughness map to the specular map input. Put that into the roughness connection instead.

kurylo3d

of course, but thats not the issue. The roughness map generated with quixel has color information in it.. its not greyscale. Roughness maps are supposed to be black and white images ... totally greyscale. My question isnt what goes into it, its whats the color information all about? I should only need 1 channel to do roughness in the texture, yet every channel is different because there is actual color information.. liek one of the materials has more red in it.

EfilOne

That's because some parts of your texture are basically metallic. If you used metallic materials on your project, espetially metals like gold, bronze or titanium (as examples), you WILL have colours on your roughness map. You should check a PBR material chart, and also those amazing PDFs from Marmoset and Allegorithmic

http://www.marmoset.co/toolbag/learn/pbr-theory
http://www.marmoset.co/toolbag/learn/pbr-practice

https://www.allegorithmic.com/pbr-guide

kurylo3d

Well last time i checked.. paint isnt supposed to be metallic, but even if that is the case. What do i plug into roughness channel and metallic channel then? Is it rgb that gets plugged into both? And I already understand the theory and practice of this workflow. PBR is not hte issue. The confusion of a texture labeled "roughness" which should be a greyscale image is the issue.

So again, if thats somehow a metallic texture in there somewhere too.. what part is metallic and what part is roughness? because i have multiple materials in there.. and that means some of it should be black for metallic, yet the majority of it is a bright greyscale with some sections having some red colors. SO.... yea.... to say its metallic just doesnt work for me. Cause that means ud be making rubber as metal lol. and wood as metal... the paint part has the red colors.

Also you just said that there are colors according to those links in the roughness channel. Hate to tell you.. roughness is also greyscale in your links. So your wrong. In your links roughness is called "microsurface".

Dklang

how do you set quixel for unreal?

kurylo3d

I set it to the unreal 4 preset or whatever.

teddybergsman

Hi kurylo32,

You are correct, roughness maps should absolutely be grayscale. Some source materials use the same bitmap for specular masking as well as roughness for performance reasons, and since metallic specular reflections may exhibit color this color information gets loaded into the roughness channel. Thanks for spotting this -- now updating the UE4 profile (and others) so that they will ensure the output is always fully grayscale.

- Teddy