Brecht wrote: "So perhaps there's still toggles needed to control if these operations should happen on premul/key alpha (for image load/save, and for color correction nodes)."
+1. I still believe this is fundamentally mandatory. Matt wrote: > That infamous Adobe thread has interesting background info in there, but I > think it's a little bit of a red herring for this issue in Blender - it's > more focused on specific behaviour that Photoshop has when loading EXRs, Disagree. The point I think that should be taken from it is that in a fully straight alpha system, it is impossible to deliver the functional range of associated alpha without workarounds. If we are discussing the merits of using an internal representation of alpha, it might be prudent to learn from the downsides of an unassociated alpha system. This is echoed by Larry Gritz (Open Image IO architect): "I am not completely without sympathy to apps that started out life with unassociated values. Color+mask is analogous to loading your airbrush with a certain color paint, and spraying it with a mask covering some areas. So for a painting app designed a long time ago (few bits per pixel, no floating point, and no experience with image synthesis), it was a representation that made some sense, and allows independent manipulation of the mask without losing precision in the color channels. But it doesn't make much sense these days, IMHO. Image synthesis used the cleaner abstraction, painting did not." [Citation pending as index isn't updated] > The advice I got from the comp lead on my previous project was that his > recommended convention for working in Nuke with premultiplied inputs was > always to manually un-premult before any colour/filtering operations and > premult back again at the end of that chain before over-ing with other > imagery. [...] > With this in mind, at least for the compositor, I'm sympathetic to the idea > of making the correct behaviour the simplest, and default, especially in > Blender when there is probably a smaller proportion of imaging experts who > understand this well in the userbase. As long as this doesn't hand cuff an artist. If it does, it makes more sense to go with added complexity and force the artist to learn the ins and outs of alpha for certain operations. TL;DR: Toggles +1 With respect, TJS _______________________________________________ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers