I switch to OCIO and the speed drops 4 times

[piotrus3333]

https://docs.chaos.com/display/CRMAX/Tone+Mapping+Operators

Care to elaborate?

From the docs I see:
Applies approximate ACES Output Transform, which consists of Reference Rendering Transform (RRT) and Output Device Transform (ODT). Value range: from 0 to 1.

How is this different from a curve?

just click the links from the docs:
https://en.wikipedia.org/wiki/Academy_Color_Encoding_System#:~:text=in%20%22RRT%2BODT%22.-,Reference%20Rendering%20Transform%20(RRT),-%3A%20Converts%20the%20scene
and read. google if necessary.

y=x/(x+1) is a curve
y=x/(x+0.187)*1.035 is a curve
Hable's tone mapping formula from Uncharted 2 is also a curve.

and this is how code for ACES RRT apparently looks (source: FilmLight):

[James Vella]

Yes I did check the links for the RRT and ODT. The Corona docs say its approximate mapped to 0-1, so thats a curve right?

[piotrus3333]

still not a curve.
you can compare it to a very precise 3d lut.

[James Vella]

you can compare it to a very precise 3d lut.

ah ok, interesting. Thanks for the information!

[Yuriy Bochkaryov]

The speed difference is drastic and shall be investigated too. For this, again, please attach the sample scene where we can do some tests.

Hi Aram
here are the scenes with pictures and examples
you can do all this in one scene, but I made 3 different ones to make it easier for you to understand

https://disk.yandex.ru/d/yrJFx5C4l-9-DQ