ACES and background images

[david_slachta]

Hi everyone,

is there any way how I can make certain textures or background images not influenced by the ACES color profile? For example a backplate behind a car, or a picture of a magazine that I need to have in my render. Things like that. I know you can replace them in post, but it would just be so much easier if they were true colors in VFB already. Especially if you need to put a car (or any other object) into the backplate and do lighting to match, it's very hard to do if the backplate's colors, brightness, and contrast is getting transformed by the ACES.

Thanks for any pointers!

[seandunderdale]

Yep..background layers sit beneath the display correction, but Id love it if they sat outside that. I want my backplate to be unaffected by anything, thats the thing Im matching to.

[david_slachta]

Exactly, I need the backplate to look the same as if I open the image in Photoshop. Is there any way to do that in VFB?

And not only a backplate. But a specific object with a texture too. Like an image mapped to a plane outside the windows and similar.

[hermit.crab]

Exactly, I need the backplate to look the same as if I open the image in Photoshop. Is there any way to do that in VFB? And not only a backplate. But a specific object with a texture too. Like an image mapped to a plane outside the windows and similar.

You are forgetting that PS also has a certain color profile assigned. From what I understand, your wish is to have two separate Display Corrections—one for the Background layer and one for everything else, which makes no sense. The way to go is to use the same color profiles for both applications and utilize Raw images so that they always match.

EDIT: Check bottom post.

[david_slachta]

Yeah, of course, Photoshop is color managed as well. My point was that when you open an sRGB image in Photoshop, or a simple Windows image viewer, or web browser, or render it in VRay with good old Gamma 2.2 workflow, it will always look the same. But when you render it in ACES, it just looks wrong.

This is a problem because, for example, when a client sends me an image of a magazine to texture the 3D object with it (the image is usually sRGB), I would always get it looking "correct" when I was using the Gamma 2.2 workflow. The magazine would be rendered slightly differently of course, because you might have colored lighting shining on it, or the magazine object has reflections, GI, and such. So I would have to adjust the colors slightly in Photoshop afterwards, but it's not a big deal. Now the ACES came along and changed all that. Suddenly all the textures and background images have different colors which are not "correct" and it's impossible to use the backplate (background in VFB) as a reference when you're making lighting for a 3D object that you want to blend in with the photographed background.

So I'm wondering about 2 things:
1. ACES has been around for several years now, and I'm sure this has come up already a few times. Have the VRay developers found out some clever way to make the background images (and specific textures of our choosing) look the same in both ACES and sRGB workflows? I mean, it's all software and ones and zeroes. There must be a way to somehow compensate for the ACES color transform to bring back the sRGB colors of the textures, so they look the same as in Photoshop, web browser, etc.
2. Is there a workaround for this to for example open the image in Photoshop first, do some inverse-ACES color transform on it, and then use this inversed image in VRay ACES and have it look the same as in sRGB?

[hermit.crab]

Judging by the other thread, you wrote in, turns out a proper "independent" way of color transforming the Background layer is already implemented (notice the Color transformation options at the bottom of the Background layer). The default OCIO or Manual with RGB Color Space set to sRGB and transform set to sRGB should the original look of the image. The only difference comes from the Display correction's "View transform", which I presume could be matched with the OpenColorIO for Photoshop plugin.

[fixeighted]

I just noticed this feature and this actually comes in very useful on a new project, where I'm matching the environment to camera projection of the same.

Is it a Vray 7 addition? I can't remember noticing it in previous versions. In any case it solves the OP's problem

[hermit.crab]

I just noticed this feature and this actually comes in very useful on a new project, where I'm matching the environment to camera projection of the same.

Is it a Vray 7 addition? I can't remember noticing it in previous versions. In any case it solves the OP's problem

It's from V-Ray 6.

[seandunderdale]

Does this solutiuon work with the ACES 1.0 SDR-Video transform? My issue is that I love the results it gives, but it clamps values at quite a low number, and also affects backgrounds, no matter what settings I have the background on.

[david_slachta]

I tried those options of the Background layer before, but I couldn't get it to work (still not looking the same) for some reason. I'll try some more on a new test scene.

However, how would you go about it with the textures? Like in my "magazine" example above? That's why I would be interested in knowing how to do the inverse-ACES color transform in Photoshop too, as I'm hoping that if I plug a similarly transformed texture to any material, the colors will stay sRGB. Hopefully the tone mapping of such texture as well...

[hermit.crab]

Does this solutiuon work with the ACES 1.0 SDR-Video transform? My issue is that I love the results it gives, but it clamps values at quite a low number, and also affects backgrounds, no matter what settings I have the background on.

I'll discuss this with the devs.

However, how would you go about it with the textures? Like in my "magazine" example above? That's why I would be interested in knowing how to do the inverse-ACES color transform in Photoshop too, as I'm hoping that if I plug a similarly transformed texture to any material, the colors will stay sRGB. Hopefully the tone mapping of such texture as well...

This thread should answer your question. You may try the suggested workaround.

EDIT: Check piotrus3333's far more elegant solution below.

[piotrus3333]

you just need a better ocio config:
https://forums.chaos.com/forum/chaos...12#post1222812



load the image and specify that it is already aces-view transformed image.

[david_slachta]

Thanks a lot guys, I'll certainly investigate. For the moment I tried to use the options of the Background layer in VFB and I'm not sure I'm using it right, but whatever options I choose never give me the right result. Below is a screengrab. On the left is what the image is supposed to look like and on the right is the VFB in ACES. You can see it's way darker than it should be.

[david_slachta]

Alright, so with Marcin's custom OCIO file I was able to get the look exactly the same. Thanks a lot! This OCIO should be shipped together with VRay, otherwise it's impossible to get the correct looking background images with ACES...

Now I just have to see if I can use the VRayOCIO node to get the textures looking correct as well...

[david_slachta]

I'm afraid I seem to be quite lost with the texture conversion I mapped my image to a dome and I rendered it (means no more Background layer anymore). However, no matter how I set the VRayOCIO node, I can't get the render to look the same as the JPG image I mapped. Help, pls.