ACEScg white point

[cvanceAA2U3]

I was wondering if anyone could help me with an Aces color space question. Using maya 2024 with Vray, and default colormanagement settings with AcesCg. My question is, and I know the color space is using a different lut, but how can I get pure white in my scene. the highest value is always a gray. thanks.
Settings
render space acescg
display srgb
view aces 1.0 sdr video
enabled color management ocio version 2.0

[Christoph_Schaedl]

More light should lead to values over 1

[nobody_b]

if you change the mixing color space to Display Space, and set rgb to 1,1,1 you will get white displayed in the viewport.

if you switch back to Rendering Space or Data, you'll see that the real value that Maya will use for calculations is around 16,16,16 not 1,1,1

[andymc4997]

Hi @nobody_b and @Christoph_Schaedl , I know this is an older thread, but this still seems to be an issue when trying to render with ACES.

Unfortunately, neither of these are great solutions. @Christoph_Schaedl, If I simply add more light to a scene in order for certain pieces of geometry to show as true white:

1. That of course lightens everything else. This alone nixes this strategy, as we are usually happy with the look of everything else, and just want white objects to look.. well, white. 

2. The LensEffect Imager can't be used, as values now become too bright,  causing things to blow out. 

Example:

Before, with the light gray cans:

After, with things blown out:

All I did was increase the exposure of my skydome a bit. So, of course the reactionary solution is to simply reduce the Threshold value for my LensEffect, which gives me this:

... a washed out mess, which looks like I've cranked up the subsurface way to high on my shader. 

If I change the mixing color space to Display Space, and set rgb to 1,1,1, as @nobody_b suggests, I basically get the exact same result. 

So does someone have a solution for this, or are we just stuck with ACES giving us light gray for white and will always need to correct in post?

[cvanceAA2U3]

yeah I was never able to find a way to do it, except in the post response You mentioned two solutions that have been brought up. If you are doing product shots, which I am and it looks like you are, it always looks dingy. I have been modifying in after effects after.

[andymc4997]

Yeah I don't understand why this issue isn't raised more often. I have an action saved in Photoshop that does an "ok" job, using Replace Color, but of course I'm still having to sometimes mask off areas that I don't want lightened, adjust color range, etc. It's frustrating. I also don't want to go back to rendering un-tone mapped with Arnold because overall ACES does look more photorealistic to my eye. I guess we're stuck for now..

[nobody_b]

for your purpose of a diffuse geo, you should not be doing what i said above (setting values to 1 in display space, because that's 16 in rendering space, meaning the surface will be 16 times brighter than the light source, and that's bad)

you should try to understand why ACES is doing what it's doing
https://chrisbrejon.com/cg-cinematography/
it darkens the image so there's more space for stuff like specular highlights to be brighter

also, check out Khronos PBR Neutral Tone Mapper instead of ACES
https://www.youtube.com/watch?v=0oIZoSg03PY

[andymc4997]

Hi @nobody_b, thanks for your reply. 

Understanding ACES and why it darkens the images is good, but that simply doesn't solve the issue. If whites are slightly darkened to allow more space, fine. How then can pure whites be reached?

I've checked out the Khronos PBR Neutral Tone Mapper, but do not know how to use it. I've tried adding a Maya EV that points to the files on my download path from here: https://github.com/KhronosGroup/ToneMapping/tree/main/PBR_Neutral.

..But honestly I'm at a loss from there. 

[nobody_b]

Understanding ACES and why it darkens the image will make you realize why pure whites can not and should not be reached on a diffuse object
(at least straight out of the render and assuming proper exposure).
You can always do post color grading.
In my opinion, if you don't like the look of ACES, don't use it.

for the Khronos PBR Neutral Tone Mapper, download it and path to the ocio file here

[andymc4997]

Thanks for your reply. When I try to map to the config file I get this error:

Error: file: C:/Program Files/Autodesk/Maya2025/scripts/startup/colorManagementUtilities.mel line 602: colorManagementPrefs: Error: Loading the OCIO profile 'Q:/AM Design/Design Tools/Maya Stuff/Khronos PBR Neutral Tone Mapper/config.ocio' failed. yaml-cpp: error at line 206, column 75: illegal map value

[andymc4997]

Hello, 

After I've been using the Rombo Tonemapper for a while with good results and better color accuracy, of course now Rombo Tools has decided the plugin is no longer free and will charge $99 for it, plus require you to download their entire set of 32 plugins.. Nice. 

So, after revisiting this method of using Khronos PBR Neutral management instead, I have figured out how to get the OCIO file to properly load into Maya. This is great, however, now of course my texture maps aren't able to use RAW, since PBR Neutral overrides everything, including maps. Won't this cause them to render improperly? And is there a workaround/solution to implement RAW and PBR Neutral at the same time?

Thanks