ACES Output Transforms Architecture VWG Meeting #24 - August 18, 2021

Thanks @sdyer for the notes and renaming of the thread.
Thanks @jmgilbert for your insight. I think your feedback on OpenDRT will be very valuable, since you are already using it in production. I’ll DM you about another chromaticity-preserving approach which may interest you.

On my side, I have been able to do a render that should illustrate the range of values that I was mentioning earlier. This test has been inspired by this thread on AC. I had been looking for a while to render something “iconic” for the VWG (hence my lego renders for instance). And by reading the notes on Gamut Compression, I thought : what is more iconic than a can of coke ?

So I did a bit of research to get the coca-cola red values, convert them to “linear-sRGB” and ended up with an exr texture of (0.9047, 0, 0). I then lit with an HDRI (the treasure island) and a distant light. Here are the results :

Linear - sRGB render, displayed in sRGB (ACES)

Same linear - sRGB render, displayed in sRGB (OpenDRT)

I was pretty pleased with this test because it matches exactly what I saw at the studio a couple of weeks ago, especially the red bounce on the white ball. To avoid any confusion, here are the exact steps of this test :

  1. A single render in the BT.709 footprint.
  2. Which was then taken to the wider gamut working space of ACEScg (in Nuke).
  3. Each was rendered from ACEScg through their respective transforms.

Regards,
Chris