I would assume all textures are converted into Linear for the shader math operations. Then lighting/PBR pipeline would work into that larger colour volume for the benefits to be seen (is that right B ?)
B - is it in the roadmap to support other/user ACES LUTs ? I have colleagues using ACES in film pipelines who would love to apply advanced LUTs to get 1:1 looks across the two industries. In another example I could have a professional colourist work on an EXR frame dump and I could pull that work back over to UE4.
ACES and Rec2020 are not just about brightness dynamic range but also about chromatic range/gamut. With the right display you will be able to see stronger more saturated colors than you could on a regular monitor or tv.
You can get an idea of this when you read about aces/rec2020 and see the horse shoe shaped color wheel with the different boundary triangles inside for comparisons.
So only lighting on old texture pipelines would not get you all that you can have for HDR displays.
Presumably like you suggest there could be a lut that can transform an sRGB’ish color space to something like the wider gamut. But you would loose bits of fidelity in both chromatics and luminance as you are stretching out colors and ‘bending’ out baked in luminance curves and clipping(rec709/srgb gamma and white points).
I assume like for all color work the better your source material the better the potential result. So if you had HDR/wide gamut acquisition and a non destructive pipeline feeding say exr’s as textures to Unreal then that should give you the best results. You’d probably want to have your paint software supporting this and a hdr display for the artist making assets.
Currently I am trying to figure out how ACEScg would be different from a regular old fashioned linear exr/data.
I’ve played around with two separate projects and have a question. Both image go very blown out and super saturated once I run through the CVars you mentioned and activate HDR output. The first project I had tweaked before hand to purposefully blow out the dynamic range so it would, in theory, map into an extended dynamic range nicer than if I had kept things tone mapped to below 1.0 but once I tried my second scene I’ve found similar results.
Do I need to prepare the Post Process Volume to do anything specific for HDR or should I make it ‘nice’ in the regular mode and the HDR output will transform things up into shape ? Just not sure if I need to compensate for the transform, or what the transform is doing. I feel that UE4 has a natural and fairly heavy tonemapper by default (that has changed a bit in 4.15) but could you advise further ?
Also did you find the missing documentation anywhere ? (so I don’t have to bother you)
Hi ,
If I can suggest another resource for ACES info/conversation: ACESCentral.com. It’s the official ACES Forum, monitored by many in the industry as well as technical staff from the Academy. Just started a new thread on Video Gaming since Unreal built in support for ACES in 4.15 and NVIDIA is using ACES for it’s HDR work.
Might help with any questions for which you’re looking for answers.
