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Renders Missing Pixels/Grainy Only in Photoshop

jsdeacon9jsdeacon9 Posts: 3
in Technical Help (nuts n bolts)

I've noticed this weird problem lately: my renders look grainy/pixelated in dark areas but only in Photoshop. They look fine in other image viewers. This happens whether I have Post Denoiser on or off. I have an RTX 3090 TI with the updated driver. I'm also rendering to .png files. When I add a layer underneath and fill it in with black, the pixels go away and it looks like it should look. Any idea what could be causing this? Is this just a Photoshop issue? I'm posting here because it seems to only be happening with Daz renders and not other .png files.

Test C.png
858 x 1026 - 487K

Comments

  • NinefoldNinefold Posts: 256

    Those areas appear grainy because they're transparent. Other software is showing them to you over a black background, so they look normal; Photoshop is showing them to you over its white-and-grey check background, so they look like noise until you provide a black background. This bug happens sometimes when the dome is off and there's an SSS material in the scene that's set to chromatic (though the effect won't always be confined to that material). I actually thought it had been fixed! I haven't seen this one myself in ages. Anyway, turning on the dome will probably fix it for future renders. In this case, it looks like if you merge this image down onto the black background you added to it in Photoshop, the resulting image is "correct" and represents what your render would have looked like without this bug, so you probably don't need to rerender if you don't want to.

  • crosswindcrosswind Posts: 6,977

    What's the version of Ps that you're using now ?

  • jsdeacon9jsdeacon9 Posts: 3

    Wow, that was it. I've never had this happen before and I certainly would not have figured that out on its own. Once I turned the dome "on", the transparency vanished. It's a bummer because I don't always want it on, but I guess it is what it is. Thanks for the quick response and help!

    Ninefold:

    Those areas appear grainy because they're transparent. Other software is showing them to you over a black background, so they look normal; Photoshop is showing them to you over its white-and-grey check background, so they look like noise until you provide a black background. This bug happens sometimes when the dome is off and there's an SSS material in the scene that's set to chromatic (though the effect won't always be confined to that material). I actually thought it had been fixed! I haven't seen this one myself in ages. Anyway, turning on the dome will probably fix it for future renders. In this case, it looks like if you merge this image down onto the black background you added to it in Photoshop, the resulting image is "correct" and represents what your render would have looked like without this bug, so you probably don't need to rerender if you don't want to.

     

  • NinefoldNinefold Posts: 256

    Glad I could help!

    If the reason you want to render with the dome off sometimes is that you'd like to be able to render on a transparent background -- well, the bug might not always make itself known, so it'll probably usually be worth it to do a quick test render and see if it's an issue for your current scene. If not, the postwork fix might still be as simple as adding a black background under your figures. And if not that, you might want to check out something like https://www.daz3d.com/mask-and-multipass-toolbox, which can generate a mask you can use to remove the dome in post.

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