New transform to enable hue based curve adjustments for color grading
Works in video, log, or scene-linear modes similar to the other Grading Transforms
Implemented with a full closed-form inverse!!
Needed for typical basic color grading workflows
Doug showed a working demo in Flame, with the different options, all running via OCIO code.
Kevin asked about separation of conversion of color model vs. curves itself - Doug said it is separate, they are different fixed functions
Mark - why is there a limitation on the number of points? How would that be enforced?
Doug - on lower end graphics cards, there are limits on number of uniforms
They are dynamic transforms, not static LUT-based ops
Open to feedback on the implementation, PR is forthcoming
What luma coefficients are used? Currently using Rec.709 simple - not as simple as HSV, but not as complicated as ACES 2.0 for scene-linear. Simple chroma based approach for log and video modes
Thomas - definitely need to keep an eye on what is OCIO, and what is not. Do we need to separate things eventually? Not against the ops, just want to make sure we’re thinking about it.
Doug - yes, good to keep in mind. Want to keep it as simple ops, don’t want to compete with full blown grading applications. Just want simple consistent color management in the same frameworks.
Remi - for the dynamic transform - how is it implemented currently?
Kevin - as a guiding principle - we have the goal recently of LUT-less configs. So we should be aiming to do in OCIO what you might otherwise need a LUT for. So more like Truelight as a comparison instead of full Baselight
Sean - can this be baked into a CTL? Yes - true of all existing Grading Transforms
Mark - is this something we want to get into 2.5?
Carol - we’ll incorporate this feedback into documentation around the grading transforms and include in our town hall presentation.