Answered: Question regarding color space of textures

veteran polycounter
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Obscura veteran polycounter
Hello. This thing comes up a lot when I work with megascans asset, and I don't really understand why it is. Often times, I get the best result if I put the roughness map into srgb color space (in Unreal Engine). Especially on foliage, but sometimes on other type of assets too. Why is that? Is this normal and I miss something? From my experience, anything grayscale should be set to linear color in PBR. I am not using the quixel master material by the way.

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  • leleuxart
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    leleuxart polycounter lvl 7
    "Best result" seems subjective. Have you tested the textures in numerous lighting conditions and/or outside of Unreal to verify it's a gamma issue?

    The only reason you set grayscale textures, or anything used for math, to Linear is to tell the editor to not apply a gamma correction to put it into linear but instead use as is during the rendering process. This can break depending on the file format, since a format like PNG usually applies it's own gamma, which reverses everything. I think Megascans textures are always JPEGs though, right? Maybe try opening it up in Photoshop and looking at the values with various gammas of 0.4545 or 2.2 to see if they look more like what you'd expect for that surface type. 

    Edit: It may also just be a case of human error if it only happens with a few surfaces, since they are all still manually processed iirc. But they're quick to fix them if you can provide the jumbled name associated
  • Obscura
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    Obscura veteran polycounter
    Hi @leleuxart . Yeah I tested them in various lighting conditions in Unreal. I haven't took a closer look in Photoshop, even though they went through a packing process in it. But to close out something, they work like I described when I don't pack them too. And yeah they are jpgs. Unfortunately I can't make screenshots at the moment because I'm in the middle of renewing my pc. I'll make some comparion shots with srgb on /off after I finished putting my computer together, and installed stuff.
  • Obscura
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    Obscura veteran polycounter
    Okay, this is what I meant:
    Roughness is srgb:

    Roughness is linear color:


    I checked out how much shiny is this plant in real life, and actually it really varies, so maybe both look could be correct-ish. However... To get similar results to the example renders on the Megascans website, I almost always need to use srgb on the roughness map of them. For example, to get this guy looking similar, I need srgb on:
    https://quixel.com/assets/shFof
    I get this with a lot of the 3d plants. It isn't a big issue, because its one click to change the color space, I just wanted to know if this is intentional and there is a reason for it.
  • Synaesthesia
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    Synaesthesia interpolator
    Hey Obscura! Apologies for the wait time on a response, I'm checking in with our content team to see what's happening here. I'll update this thread as soon as I have an answer.
  • Synaesthesia
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    Synaesthesia interpolator
    Hey @Obscura! Sorry about the wait, it's been super busy for us. The long story short is that our renderings on the site are sometimes tweaked by the individual artists creating the scenes, so while the values being presented are 99% accurate in general, feel free to use a material instance to control the roughness as you see fit. Ultimately whether it's accurate or not takes a back seat to whether it looks good or not.
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