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longrayjohnson
04-12-2010, 07:35 PM
hi,

new to nuke. i got a multilayer openExr out of maya with several passes. some of them are rgb-mattes and if i shuffle out one of them and turn all inputs to RRR to separate the R-Channel i still have some of the other colors in the channel.
i tried a grade after that to key out the non full white parts, but there must be a better way.

alkali22
04-12-2010, 07:49 PM
Why not just use a Shuffle with all channels that aren't the one you want set to Black?

So if you're after the red channel, just set G, B, and A to Black (0).

If you have an RGB mask pass, however, you don't necessarily need to isolate a single channel to use it as a mask... for any mask input, you can just select a single channel from a layer to use.

kag122
04-14-2010, 10:06 AM
It's easier to avoid problems by having all of the channels remapped to one colour.

In regards to the problem.

Sounds like you haven't got all of the mattes exclusively included in red. It's most likely that you aren't rendering them out from maya properly.

Check the image values to see if they are pure red (1,0,0)

alkali22
04-14-2010, 05:05 PM
It's easier to avoid problems by having all of the channels remapped to one colour.

Not sure what your reasons are here besides purely preferential, but if you have an RGB mask pass with 3 objects in it (one red, one green, and one blue), there is no reason you would have problems picking a single channel as your mask source. Shuffling red into all 3 channels isn't going to solve anything or protect you from any hidden gremlins, so to speak. :p

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04-14-2010, 05:05 PM
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