[Nuke-users] How does DeepRecolor distribute a target opacity across multiple samples?
Hi, Sorry for the repost. I sent this to the development list yesterday, but posting over here as well to cast a broader net. Has anyone dug around the "target input alpha" option in the DeepRecolor node, and has some insight on how it is retargetting each sample internally? Long story short, I'm trying to implement a procedure to re-target opacity of each sample in a deep pixel, akin to what's happening in a DeepRecolor node when "target input alpha" is checked. I've got this to a point where it's working ok, but I think I might be missing something, as my results differ from those you'd get in a DeepRecolor. My re-targetting algorithm is based on the assumption that the relative opacity between samples should be preserved, but DeepRecolor clearly uses a different approach. Example: Say you have a deep pixel with 2 samples, and the following opacities: Samp1 : 0.4 Samp2 : 0.2 The accumulated opacity is 0.52 (Samp1 over Samp2). Note that Samp1 deliberately has an opacity of 2 times Samp2. Now, let's say we want to re-target those samples to an accumulated opacity of 0.9. What I am doing is trying to calculate new opacities for Samp1 and Samp2 in such a way that both of these conditions are met. a) Samp1 == 2 * Samp2 b) Samp1 over Samp2 == 0.9 This gives me the following re-targeted values: Samp1 : 0.829284 Samp2 : 0.414642 I'm happy with those, but it bugs me that DeepRecolor throws different results: Samp1 : 0.798617 Samp2 : 0.503434 Which meets the second condition (Samp1 over Samp2 == 0.9), but does not preserve the relative opacities of the original samples. It seems to me like DeepRecolor is applying some sort of non-linear function to apply a different weight to each of the original samples, but I haven't been able to figure out the logic of that weighting, or a reason why it's done that way. Does anyone have any insight/ideas on what DeepRecolor might be doing internally? Or a reason why you might want to distribute the target alpha in a non-linear way? Thanks in advance, Ivan ___ Nuke-users mailing list Nuke-users@support.thefoundry.co.uk, http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
[Nuke-users] Disparity
Hey Nukers, I do have to expose my stupidity. I do not fully understand the concept behind the disparity channels in nuke and how we should feed them from 3d. We do have a shader that calculates the pixel distance between left to right eye and from right to left eye. Those get rendered in the according eyes. So the disparityL.x channel contains "left to right" in the Left image and "right to left" in the right image. Now looking at nukes disparity setup I came to the conclusion (which I am questioning a lot), that the disparity needs to go into the channels disparityL.x (we only have x difference) for the "left to right" stuff from the left eye and in the disparityR.x I copied the "right to left" from the right eye. looking at that from the left view it all makes sense, so my next conclusion was that the "right view" of the disparity channel (which is the sum of disparityL and disparityR) does not need to have a "right view" or should the right view be the same as the left view... The reconverge node behaves as expected but I am not sure how the disparity is supposed to look like from the right view. So the questions are: Does disparityL look the same through left and right eye ? Does it need to have a right eye ? or can the right eye be black ? Does disparityR look the same through left and right eye ? Does it need to have a left eye ? or can the left eye be black ? This all leads to the question is disparity "monoscopic" in nuke ? with all that came another question if one can access the "other eye" in the expression node ? like disparityL.left.x (I have tried some combinations without success) Or is there somewhere a page that explains all that ?? Thanks in advance for enlightening me. Cheers Johannes -- STUDIO RAKETE GmbH Johannes Hezer, Compositing TD Schomburgstr. 120 D - 22767 Hamburg j.he...@studiorakete.de Tel:+49 (0)40 - 380 375 69 - 0 Fax:+49 (0)40 - 380 375 69 - 99 -- Pflichtangaben laut Handelsgesetzbuch und GmbH-Gesetz: STUDIO RAKETE GmbH Schomburgstr. 120 D - 22767 Hamburg www.studiorakete.de / i...@studiorakete.de Geschaeftsfuehrer: Jana Bohl / Hans-Martin Rickers Die Gesellschaft ist eingetragen im Handelregister des Amtsgerichts Hamburg unter der Nummer HR B 95660 USt.-ID Nr.: DE 245787817 ESET 8964 (20131025) The message was checked by ESET Mail Security. ___ Nuke-users mailing list Nuke-users@support.thefoundry.co.uk, http://forums.thefoundry.co.uk/ http://support.thefoundry.co.uk/cgi-bin/mailman/listinfo/nuke-users
