Help Topic: OCIO and LUT

[piotrus3333]

ok - I think I stand corrected on automatic gamma in 2015 - seems to work just fine - but I'm 100% sure it used to be wrong at some point so I'm saving my exr's with override to 1.0 option. just prehistoric habit I guess so sorry for confusion here.

the rest is ok, but I might have explained it a bit clumsy so lets do that with 3 images:
linear render in vfb
with applied filmic tone mapping in vfb (copied and pasted to ps)
32 bit exr from vfb with lut in ps. lut saved from vfb containing filmic tonemapping via lut from Adanmq

difference in very bright areas is probably due to the way ps handles luts. its just ps after all so don't expect too much here.

[kosso_olli]

Why saving out the LUT from the VFB? Doesn't loading the Adanmq LUT in PS give the same result?

[piotrus3333]

Why saving out the LUT from the VFB? Doesn't loading the Adanmq LUT in PS give the same result?

i guess 'convert to log color' is missing

[kosso_olli]

I tried this. How do you save out a LUT from VFB that is readable by Photoshop? I get a vcclut from VFB, I can not load this is Photoshop.

EDIT: Found it under Globals at the top, you can select cube format for saving. However, the result in PS is totally different.

[Vizioen]

I tried this. How do you save out a LUT from VFB that is readable by Photoshop? I get a vcclut from VFB, I can not load this is Photoshop

At the top you can save out al the color corrections to a cube in the extension selection dialogue dropbox you can select lut. If I use this in photoshop though my image gets washed out, probably because there's an sRGB correction too or something.

[sharktacos]

V-Ray can load the Filmic Log base OCIO, but it does not allow you to use OCIO and LUT at the same time.

Question for Vlado and the Chaos crew: Would it be difficult to make the VFB able to read an OCIO config and a LUT simultaneously? It would be good to have that flexibility I think.

[vlado]

Question for Vlado and the Chaos crew: Would it be difficult to make the VFB able to read an OCIO config and a LUT simultaneously? It would be good to have that flexibility I think.

Not right now, but this will be possible in VFB2 (our new implementation of the frame buffer).

Best regards,
Vlado

[yolov]

That's already on our to-do list, but we haven't gotten there yet. I've logged your request to the same task.

[OPEN_RANGE]

VFB2? Here is a wish list item for that:

https://forums.chaosgroup.com/forum/...ge-fit-for-vfb

[sharktacos]

Not right now, but this will be possible in VFB2 (our new implementation of the frame buffer).

Best regards,
Vlado

ooooh, VFX2! Sounds like some good stuff is cooking. Looking forward to seeing what you guys come up with!

[sharktacos]

- Yes, it is a LUT, technically, but LUTs can not access more than 0-1 range, so that LUT needs to be fed the source image in a Filmic Log base, instead of sRGB base, so it can access entire exposure range, not just 0-1. And this is something V-Ray can not do. V-Ray can load the Filmic Log base OCIO, but it does not allow you to use OCIO and LUT at the same time.

What would be an experiment that would demonstrate this? When I have applied OCIO configs like spi-anim and ACES, and compared this with a .cube LUT of the same, I have not seen any difference.

[sharktacos]

As discussed in this thread, it is currently not possible to use a LUT and OCIO config simultaneously in the V-Ray VFB. However, I was able to modify an OCIO config to define additional color space displays which add a desired "look" and I thought I'd share it with you lovely people.

The following modified spi-anim OCIO config includes two additional "look" displays, one using a CDL .cc file and another using a .cube 3d LUT file. First download the spi-anim-look config and unzip it.
http://docs.sharktacos.com/images/tu...-anim-look.zip

Next you will need to create the desired color grade in Nuke. This should be done with the spi-anim OCIO config applied in Nuke so you are viewing your render through the "Film(sRGB)" view transform. You can create your "look" color grade in one of two formats.

1. ShowCC: Use a OCIOCDLtransform node to make your desired "look" color grade and click the "write .cc" button saving the file in the "lut" folder of the config, overwriting the "show_cdl.cc" file. Load the spi-anim-look and select the "ShowCC" display transform to see your .cc "look" color correction file.
2. ShowLUT: Create your desired "look" color grade using whatever nodes you like (ColorCorrect, Grade, etc.) and create a .cube lut file (using the CMStestPattern and generateLUT nodes). Saving the file in the "lut" folder of the config, overwriting the "show_lut.cube" file. Load the spi-anim-look and select the "ShowLUT" display transform to see your .cube "look" LUT.

Note this is all "as is" with no warranties, but if folks have suggestions for how to make it better I'm happy to learn. Hope it's useful!

[MANUEL_MOUSIOL]

I just discovered this thread.
sharktacos your OCIO sounds very very interesting! Thanks for sharing, first of all!
I dont use nuke and have a few LUTs that I like to use but have to bring the rendering to a very flat log space first so I can savely apply the LUTs.
I tried out your OCIO but am a bit confused about how to use it exactly with the LUTs I already have.
I renamed my cube LUT to "show_lut.cube" and overrode the original file in the LUT folder. What about all those different input colorspaces?
Do I turn display in SRGB color space off?
When choosing ShowLUT the colors get all weird magenta. what am I doing wrong?

I am sorry, I didnt read all 7 pages of this thread and maybe I missed something.
Greatful for any pointers.

[sharktacos]

It’s hard to say. I do note that you say you work in log space. I would not. I’d render in linear space and save in EXR. The OCIO config is designed to work that way.

As far as the look LUT, try making a LUT that’s really obvious (like all black and white or something) just to confirm that it’s really reading it.

[MANUEL_MOUSIOL]

yeah, I am still working on a good workflow that is fast but goodlooking. I would love to get most of it done in VFB to quickly be able to send out previews, instead of having to go to Photoshop or so everytime...
I am using Kim Amland - Photographic LUTs, so there is no color in it...