Kevin Wheatley: We'll mostly be discussing tidying up, matching CTL and Blink. We talked about having a Blink version of the release in a separate directory.
Scott Dyer: I pushed a bug fix to the CTL, but it doesn't change anything.
Kevin Wheatley: The CTL comments mention possibly adding the extra LUT entry, but you haven't done it.
Scott Dyer: I tried at one point because other math needed updating to make it work. I was aiming to match Rémi's Python(with updated parameters) as a reference. I plan to add it at some point.
Kevin Wheatley: We were discussing bug fixes vs changes.
Scott Dyer: We don't want to do more parameter tuning. Anything we add needs to be justified and explained to the developers. Steve and Alex talked to developers at NAB and plan to continue to assist them.
Kevin Wheatley: It would be good to have a target date for creating documentation.
Scott Dyer: I have been writing an explanation of the changes from ACES 1. What we changed and why. Then there needs to be documentation of what the transform does and howe, leveraging what Nick and Pekka have already written, for those who want to go deep. Also some user centric guides, showing the ODTs we've created and how to make custom ones. What the parameters do.
Kevin Wheatley: Yesterday[in the OCIO TSC meeting] Carol asked if there would be additional LMTs that OCIO would need to implement.
Scott Dyer: There is a plan to have some creatives create some LUTs. I am not yet sure how those will be converted to CTL or CLF. Ideally they would be broken down into mathematical operations, rather than being a single 3D LUT. That's hard to do from proprietary grading tools.
Nick Shaw: If the are CLFs, there is no implementation for OCIO to do. They can just add them to the repo.
KE: Exactly. Are they part of the ACES release, or can we point to where they are without caring what's in them?
Alex Fry: Mathematical looks would be nice.
Scott Dyer: But then what tools do we give people to create them?
Nick Shaw: There are no tools for building CLFs. I thought about building some DCTLs equivalent to the types of CLF process nodes, and then if a look was built only with those, it would transfer one to one to CLF. But that doesn't give colorists a nice UI connected to a control surface. The current ACES 1 contrast LMT is CTL?
Scott Dyer: Currently CTL but easy to make a CLF.
Kevin Wheatley: So the priorities are matching the CTL in Blink, and documentation. The implementers need to know if the looks are required for ACES compliance.
Scott Dyer: That is a point of confusion with the logo program. Not everything that supports ACES has to support CLF if LUTs aren't a function of their tool. Only what is applicable. That's better than forcing everyone to implement everything. We want to make it easy for people to add more things later.
Kevin Wheatley: The only complex transform we should consider is a full 1.2 emulation. We can show the improvements, but for those who prefer the previous version we have an LMT. In CTL you could make it out of forward and reverse old and new transforms. But implementers could simplify that. OCIO could optimize it down to the old transform. Going back to the Blink. How do we make it match the CTL. Do we just match Scott's parameter name changes? Or do we start from scratch and back port?
Alex Fry: A full match would be nice but is a lot of work.
Nick Shaw: Does the CTL do any extra pre-computing that the blink doesn't, such as the surround stuff?
Scott Dyer: I left that in because I was using the surround parameters in the dark to dim. But we're not doing it that way any more. I am sure the CTL could be optimized more, but some I kept for readability. I created a params structure like Rémi did in his Python.
Kevin Wheatley: In Blink it's not practical to put sub-functions in separate files as the CTL does. I did put encoding and decoding in separate nodes, so the DRT is XYZ to XYZ.
Scott Dyer: I wrote the CTL to can help with updating Blink, but I am not great with Blink.
Kevin Wheatley: Blink is not always easy. Has anyone verified Rémi's Python matches the Blink.
Scott Dyer: I tested to a certain extent when writing the CTL.
Nick Shaw: Rémi's Python is still at v55.
Kevin Wheatley: Things may match with normal images, but our recent changes have been about edge cases. We need to create test cases. They would be useful for implenter anyway.
ACES Output Transforms VWG
Meeting #150, May 1st, 1pm PT
[Meeting Recording]
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