ACES ocio and Maya SynColor

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Derek Flood

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Jul 24, 2017, 9:54:53 PM7/24/17
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So I ran into an issue with the OCIO ACES 1.0.3 config. In the image below you can see that the ACES transform is getting large "highlight" on the magenta and blue spheres. This is not the specular highlight, but the diffuse color at a high value (around 4). In comparison the spi-anim config does not have this issue.



Doing further testing I compared the ACES in OCIO with ACES in Maya's SynColor. In the image below the blue sphere on the left is using ACES 1.0.3 in OCIO which again has the error, and the sphere on the right is using ACES in Maya's SynColor. In both cases the render is the same, the only difference is the display transform. For the OCIO it is "sRGB", and for SynColor it is "ACES RRT v1.0."  I believe the file that the file used for the synColor  "ACES RRT v1.0" display transform  is ACES_to_sRGB_1.0.ctf



question#1: How can I convert the Maya SynColor .ctf file into something that the OCIO can read?  I don't think that ociobakelut can read .ctf files. happy to be wrong about that.

question#2: Is there an OCIO config for ACES that is the same as the one used in Maya 2017 SynColor?








doug

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Jul 27, 2017, 1:02:09 PM7/27/17
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Hi Derek -

Yes, you're running into a known issue with the ACES OCIO config -- as colors get very bright they start to lose accuracy. A lot of great work went into the ACES config, but it does run up against the limits of the current OCIO ops.

The ACES OCIO config bakes the complex math of the ACES transforms into LUTs and this is a common problem with that approach -- certain colors are not reproduced accurately. The Autodesk SynColor engine, and its native CTF format, were designed to be able to represent and apply the ACES transforms in a more exact way.

So to answer your first question, if you were to convert the CTF into something OCIO can currently read (such as by baking it into a 3d-LUT) you would have the same type of problem you're currently having with the OCIO config.

Regarding your second question, there is currently no way to represent the Autodesk ACES implementation in an OCIO config. However, we are exploring some ideas that may help in that regard so please stay tuned.

best regards,

Doug Walker
Autodesk

Derek Flood

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Jul 27, 2017, 2:29:50 PM7/27/17
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Thanks Doug. That would be great to have OCIO be able to do that. Looking forward to what you guys come up with!

Patrick Hodoul

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Jul 28, 2017, 12:46:12 PM7/28/17
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Try to be at  "SIGGRAPH 2017 - OpenColorIO Birds of a Feather" if you can...

Patrick
Autodesk

Dithermaster

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Jul 28, 2017, 12:48:26 PM7/28/17
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Plz livestream it!

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Dithermaster

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Jul 28, 2017, 12:50:37 PM7/28/17
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Google tells me it is:

OpenColorIO Meetup
Tuesday, 1 August, 1:00 pm - 2:00 pm, Los Angeles Convention Center - Room 507
Updates on the status of OpenColorIO (OCIO) and a chance for in-person dialog among OCIO developers and users.

Steven Varga


Also, this should be of interest:

ACES Next: Help Design the Future of the Academy Color-Encoding System
Wednesday, 2 August, 9:30 am - 11:00 am, Los Angeles Convention Center - Room 406A
ACES 1.0 is widely used in the VFX industry. Join the effort to enhance and extend this important industry standard to meet your current and future needs.

ACES Team (c/o Steve Tobenkin)

Jared Keller

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Jan 29, 2018, 8:24:54 PM1/29/18
to OpenColorIO Users
Did anything come of this discussion?

Jared
Blizzard Entertainment


On Thursday, July 27, 2017 at 10:02:09 AM UTC-7, doug wrote:

Deke Kincaid

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Jan 29, 2018, 11:32:42 PM1/29/18
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Which one? 

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Sean Cooper

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Jan 30, 2018, 3:21:31 AM1/30/18
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Yes, the discussion had unfortunately been carried over to the OCIO developers forum and not mirrored here in the users group.


Which one? 

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