ACEScg for Animation feature and further questions

rendering space is ACEScg
display space is P3D65 (it is a screenshot)
redcolor is 1/0/0 in Rec.2020

I’ll keep my investigations going. Thanks for your help. :wink:

Hmm, maybe I’m not understanding you correctly, but I think the color should not exceed 1/0/0 in raw. If it is 1/0/0 in Rec.2020 then I believe that would mean its above 1 in raw which would make it emissive.

Hum interesting… But what is raw? I had understood that there is no such thing as raw. Or should I ask: what color space is raw? :wink:
Our guess is that the ODT actually struggles to bring back extreme values (like imaginary ACEScg primaries) into the P3 gamut… Still investigating. Thanks !

@ChrisBrejon by raw I meant ACEScg (that is, the working/rendering space). You had said Rec.2020 which is of course close to ACEScg, but it struck me as odd. So I thought it may be something to check.

Then again, ACES does seem to have a hard time with saturated colors. We know it has a hard time with blue and yellow. So maybe you’ve discovered an issue with red…

ACES reminds me of driving a race car, where the slightest turn of the steering wheel can send you crashing into a wall. ACES likewise seems really sensitive. I think as it grows into more widespread use it will need to develop seat belts and bumpers so it’s not so easy to make errors.

One of those error prone places for me has been in picking colors. That’s why I set the color picking role in our OCIO config to ACEScg to prevent that. I really think they should change that in the official OCIO config. Having it set as Rec.709 makes it almost inevitable that users will pick colors with values above 1. Because the display transform applies a tone map curve to the output image, a value of 1 in sRGB or Rec.709 space will remap to a value of around 10 in ACEScg linear space. In other words, if you pick a color like pure red for your diffuse texture in Maya then the RGB values of <0,0,1> will actually give you pixel values in your render of <0,0,10> making your shaders light emitting which breaks the PBR rule of energy conservation which states that an object cannot reflect back more light that what is shining on it.

Check the pixel value of the red in your rendered image and see what it is. I bet it’s really high (like above 10) which is causing it to clip.

Thanks for your answer. :wink:

yes it seems to be the case.

I agree on this as well.

True. I think it is like this by default in the config so people pick the color they want to see.


I have done this test in Nuke. Working space is ACEScg. 1/1/1 values give 16.29/16.29/16.29 with the reversed ODT.

Another test here. Working space is ACEScg. 1/0/0 value give 1.24/0.10/0.01 with the reversed ODT.

It is 1/0/0. I have been not clear enough. The test I have provided is using a color picking role in Rec.2020. But the issue is the same with a color picking role set to ACEScg. There is no conversion involved here.

I do have issues of banding with a Red 1/0/0 set in Raw (ACEScg in this case). And since you use a color picking role set to ACEScg as well, I was wondering if you had faced the same issue.

Hope I have better explained this time. I am really not talking about a color picking conversion that would give values above 1. I am really talking about an ACEScg primary not displaying correctly in P3 once it is lit. No light emission here.

Thanks for your help!
Chris

Thanks for clarifying. I don’t have a monitor in P3 so I’m not able to test that. Hopefully someone else can jump in.

Thanks for your help. i am pretty sure we would have the same issue in Rec.709 or sRGB (ACES). Thanks !


Hi everyone, I have uploaded my albedo chart with RGB values and a few corrections as I am using the color checker 2014. All the best for 2020, Chris

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Just replying here to myself as it could be useful. :wink:

The less saturated look is completely normal. In our previous workflow, a sRGB primary would be displayed with no transform on a P3 monitor. With ACES, since it is color managed, the same linear-sRGB render would look less saturated on the same P3 monitor.

This is one of the great things I have learned thanks to this community. :wink:

You can build a custom ODT for a display and have it show a more wider range of colors ?

How are you getting D65 white point, what method are you using to calibrate ?
I’ve tried with DisplayCAL and I can’t get that D65 white point; I know it’s possible but seems like a fight.

I don’t remember exactly how we calibrated. We had these NecPA302W monitors that were calibrated by someone at the studio. Probably like this.

Chris