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OCIO workflow very slow.

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houou
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OCIO workflow very slow.

#1

Post by houou »

Is there an OCIO node that is multicore, or another way to convert to ACEScg (or ACES cc ) that is not so costly.
we are working with some really really big renders 10.000x5000 and the process to change from Lin.sRGB to ACES takes a while... and color corraction is very anoying.
Of course we can reduce to work more confrotable but still... just wondering if there is another way to go and back from ACES in a faster or multicore way.

Thankyou!

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Midgardsormr
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Re: OCIO workflow very slow.

#2

Post by Midgardsormr »

I haven't tested it to be sure it's accurate, but the Gamut tool has an ACEScg mode, and it's GPU accelerated.

Make sure any time you have the opportunity to request features that you mention faster OCIO tools! It's definitely a pain point right now.

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mseredkin
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Re: OCIO workflow very slow.

#3

Post by mseredkin »

Do not use Gamut in combination with aces cg, it gives an incorrect result. Sapphire S_OCIO Transform works several times faster

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Millolab
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Re: OCIO workflow very slow.

#4

Post by Millolab »

mseredkin wrote: Fri Jun 18, 2021 3:23 pm Do not use Gamut in combination with aces cg, it gives an incorrect result. Sapphire S_OCIO Transform works several times faster
I’ve been using the Gamut node for AcesCg and it seemed correct to me... am I missing something?

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houou
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Re: OCIO workflow very slow.

#5

Post by houou »

I see sapphire is a way.

Tried Gamut, was faster, but result was different....
How you people use Gamut so it looks like OCIO result?

thank you!

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danell
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Re: OCIO workflow very slow.

#6

Post by danell »

You need to use the gamut in combo with the CineonLog node. So footage -> CineonLog -> Gamut, to get the same result as OCIO.
CineonLog changes the Gamma ("luma"), Gamut changes the gamut ("color")

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houou
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Re: OCIO workflow very slow.

#7

Post by houou »

Oh!!! I see, that makes lots of sense I'll give a try, thank you!

Added in 22 minutes 6 seconds:
I'm giving it a try but struggling with the settings.. I cant get a consistent round trip


1. CineonLog ---- lin to log ( ACESlog )
2. Gamut ---- source no change / output ACEScg ?¿
3. here will come the CC if needed.
4. 2. Gamut ---- source no change / output sRGB ?? (but idealy would be linear here right)
5 CinenonLog ---- log to lin (ACESlog)

and everything is a big mess.... :S

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danell
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Re: OCIO workflow very slow.

#8

Post by danell »

What DIT and ODT are you picking in OCIO for all the footage?

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houou
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Re: OCIO workflow very slow.

#9

Post by houou »

my footage is linear, comes from vray is a CG render and I don't do anything with it as for start.
For output, sometimes we do Linear because it goes to some other place but most often sRGB.

Is that what you where asking for? :D not sure.

In the OCIO node I was setting up from lin to ACEScg or ACEScc do the CC and then ACEScg or ACEScc to sRGB.
Was this even correct? the colors I could achieve

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danell
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Re: OCIO workflow very slow.

#10

Post by danell »

IDT = Input Device Transform (in your case I'm guessing linear sRGB)
ODT = Output Device Transform (sRGB with 2.2 gamma to view on your monitor or linear sRGB for your delivery)

In your point 1 and 2, what are you converting from linear to log or are you going 100% CGI?
If you're going 100% CGI then use this setup:
1. Add a gamut node to your CGT from sRGB to ACEScg with Remove/Add Gamma UNchecked and Pre-Divide/Post-Multiply checked
2. Do your comp.
3. Add a gamut node to your CGT from ACEScg to sRGB with Remove/Add Gamma CHECKED and Pre-Divide/Post-Multiply checked

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houou
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Re: OCIO workflow very slow.

#11

Post by houou »

So you are saying that I shouldn't use the Log to Lin just the gammut?
But that gives very different results from the OCIO node :\ and how the gain affects the waveform is also not like "ACES" like.

I'll do some captures but so far not too much luck with this :(

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Re: OCIO workflow very slow.

#12

Post by Midgardsormr »

mseredkin wrote: Fri Jun 18, 2021 3:23 pm Do not use Gamut in combination with aces cg, it gives an incorrect result.
I wanted to quantify this assertion, so here's the result of an experiment:

Image

Image

The OCIO and Gamut nodes definitely produce different results. My color science is not up to snuff, so I'll leave it to someone else to evaluate what's going on here, but the clamping that the OCIO node does is concerning. Granted, there are negative values there, but it's good to know that the conversion will throw away data if you're not careful with it.

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danell
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Re: OCIO workflow very slow.

#13

Post by danell »

I'm getting the exact same image from CineonLog+Gamut as OCIO.
@houou Can you share a frame of each of your plates and a printscreen/comp with your OCIO setup for each of the plates?

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cinewrangler
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Re: OCIO workflow very slow.

#14

Post by cinewrangler »

Once I had to write an OCIO node for some software application... based in that I can say that many conversions inside OCIO are done using LUTs. And LUTs using linear data is input is a bad idea. I'd guess that internally they first apply some log curve and then run the data through the LUT. But anyway, you don't get "calculated output" but instead "interpolated output". And the input to the LUT is some restricted range, so expect some clipping/clamping.
On top of that (at least with the OCIO version we used back then) the provided OpenGL functionality used trilinear interpolation compared to the tetrahedral that the CPU path is using. This is probably not an issue in Fusion (where I'd expect it to use only CPU anyway) but I've heard that some people noticed a difference between OCIOs CPU and GPU processing.

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houou
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Re: OCIO workflow very slow.

#15

Post by houou »

Right is the Vray exr with ACES enbebed + srgb gamut for preview on screen. I have also an JPG of that that has also the SRGB enbebed and looks exactly the same.

Then, right, in the first image is OCIO workflow, it looks almost identical, just there is some slight exposure variation this could be due to Vray applying slightly different curve.. but the CC behaves exactly like it does if I do in vray. what is very convenient.
ocio_workflow_001.png

doing just some gain variance... I can get the difference almost showing black. despite a slight blue in the grass ( I saw that Vray offers a ACES blue fix ) not sure if that could be the issue with the blue.... but well... close enough.
ocio_cc_difference_workflow_001.png

In the second image is only with the gamut, and the result is quite different specially on the bright areas, of course could be color corrected, but how the CC behaves is very different from what it does under OCIO workflow.
gamut_only_workflow_001.png

I also made a ZIP with everything just if somebody want to give a look.

Thank you!
aces.zip
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