How does VRay prevent texture discoloration in the ACES color space

[seandunderdale]

Isnt his first post only about trying to get two blues to match?

[piotrus3333]

Isnt his first post only about trying to get two blues to match?

blues do not match because OP is not translating the blue texture the way he is translating the colour swatch input.

screenshot 1: swatch input (I'm assuming Cinema expects acescg here) with inverted aces display transform.
screenshot 2: input texture is tagged as BT.709 ("sRGB") colour space with sRGB transfer function.

two different shaders as well but my guess is it should not matter in this case.

[piotrus3333]

this is not really colour management problem but linear workflow mistake.

[seandunderdale]

I take your point, but this thread going on as long as it has suggests its hard to follow for a lot of artists.

[piotrus3333]

I take your point, but this thread going on as long as it has suggests its hard to follow for a lot of artists.

well.
those artists are being paid to know what they are doing. introduction of wide gamut rendering space in VRay is just a feature. use it if it works for you - if you have no time for it - just stick with what you know as you most likely do not need it.

[piotrus3333]

I take your point, but this thread going on as long as it has suggests its hard to follow for a lot of artists.

ok - as you mentioned - you are (I assume, again) using acescg as your rendering space in VRay - what resource would you recommend to learn about it?

edit: single resource if possible, manual, video tutorial - whatever.

[seandunderdale]

I dont know a single, solid resource (yet) for how to manage aces in vray / maya. Maybe Ive not found the correct vray docs about it, but I couldnt find the info I wanted when checking. I just did a test and there is no amount of colour space changes I can find, to get a blue texture to show 255 blue in Maya / Vray, using the default colour management settings. I have to change the view transform to "untonemapped" and use a filmic tonemapper like ampas to get to 255 blue on the texture, but then there are other issue with using that method if you dont like the contrast / look and feel of ampas tonemapper.

Personally I have switched back to using the default aces / ocio settings with aces 1.0 sdr video view transform, and layering on a curve and a LUT to correct the crunchy darks. I like the way that view transform handles highlights, and once corrected it feels right to me, but if I had to do anything with "correct" colours like logos, Id be in trouble working this way I think.

[piotrus3333]

123456_

ok - if solution with VRayOCIO is not working for you - would simply using not Video SDR display transform but Un-tone-mapped look somewhat acceptable? you mentioned "engineering" and "outdoor texture" so I have no idea how PBR your work is. (any "filmic" display transform will stay within PBR boundaries so pure blue pixel is highly unlikely, even if it is a laser or something)

and if you do not really need ACES (I suspect you do not) you might look into this tone mapper that was created to solve issues similar to yours:
ToneMapping/PBR_Neutral/README.md at main · KhronosGroup/ToneMapping · GitHub