Chaos Corona for 3ds Max > [Max] Corona Goodies - User Contributions

AgX in Corona

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mienda:
 
Thank you very much for your answer Piotrus. This clarifies these tone mapping things that are still confusing for me

piotrus3333:
Another example of using AgX:
Resolve AgX version (DCTL) married to look from famous ARRI K1S1 lut.

alexyork:
Hi Marcin, folks/devs,

We are typically using your fantastic AGX ToneMapping instead of ACES for almost everything these days, from this method, as it seems to have a much more pleasant and predicable rolloff for the highlights while preserving contrast and colour. The issue we're facing is that it doesn't seem to work properly with ToneMapControl when you set it to not affect the map. It seems to affect the exposure and crush certain tones and mess around with the contrast. I see there's a warning for this on the corona website "While the Corona Tonemap Control Map works fine most of the time, there are some special cases where it may fail, for example: using some LUTs, using extreme tone mapping operator values, setting the Contrast value to zero."

- Is there any workaround for this to get 1:1 result with the underlying map, like we get with ACES workflow?
- Is there a simplified single-LUT version of this we can use, which may or may not help?

Some notes:
- corona 11 HF 2, max 2024
- base map is an SRGB photo loaded into coronabitmaploader, zero colourcorrection, just the pure map
- it's then piped into tonemapcontrol with all the checkboxes disabled
- using AGX workflow method from here: https://forum.corona-renderer.com/index.php?topic=40952.0 - it results in 2 x LUTS being loaded into the coronacamera tonemapoverride. It's the second (lower) of the two LUTs that's breaking things (or rather being broken by the tonemapcontrol). And I believe we have the correct Logarithmic settings
- contrast is at 1.0, or 1.5 it doesn't matter (but it's not at 0.0 FYI, which we know can break things)
- we're aware of the IR tone mapping bug where you need to re-start the IR each time you affect things like exposure, tone mapping, LUTS etc. which we've done, so this isn't the issue (although devs, any news on a fix for this? it's very annoying and easy to forget!). It happens also in production rendering.

Example below:



Thanks for any help!

piotrus3333:
@alexyork

skip the Corona Tonemap Control and just transform the backplate into your rendering space, linear rec709 in this case.
for this you need to reverse the AgX Punchy display transform. lin rec709 backplate will get back to AgX Punchy via frame buffer corrections. if you need to colour correct the backplate in Max do it in lin rec709 so its nice and tidy.

you need the original AgX ocio config from Troy Sobotka: https://github.com/sobotka/AgX

attached screenshot shows conversion done with VRayOCIO node, you can do this with Affinity/Photoshop/whatever else. 3dsMax 2024 setup with this AgX OCIO file should be able to convert it too.
there will be slight differences as luts I made ale limited in precision by Corona's cineon log conversion in lut layer.

piotrus3333:
you can actually also try these luts. made for Vantage so you will always end up with transfer function difference srgb vs 2.2.
I also never tested Corona's linear option in lut layer so no guaranties.
instead of log - use Reinhard curve (h compression 999 in Corona) - should be more precise compared to old double lut setup.

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