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rendering motion vector as color plane


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Sorry if this has been covered in an older post (if so, can someone point it to me).


I'm rendering a few extra image plane (C, A, z-depth, motion vector ) but I would like to export them all as separate image sequences.

Have one sequence of image with RGBA

one sequence with the motion vecot as RGB


is there a mask channel node? convert channel? convert image plane?

I tried using the channelcopy cop with the target as the rgb and the source as the motion vector, with no result.


I can't unfortunatly post the scene file.

I'll try to repro it at home and post something later.


any info would be appreciate.



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Hi Matt,

thanks for your reply and sorry if I sound dumb, but which node are you refering to?

the file node in COP?

The mantra node in the output?

I also looked in the documentation and all I could find was in the mantra node documentation ... unfortunatly, when you open houdini and put down a mantra node that check box don't exist ... or at least I coulden't find it.


But that would not help me anyway. I export my images from Maya (via mental ray). 


here is what I have:

in my COP context I added a file cop and a copychannel. but the only thing I can see as a result is the C (rgb) plane.

it works with other plane




what I see before AND after,



what I should see, even when I select C after the ChannelCopy cop...




any idea?


Is it a naming issue? my channel's name seems to have column (" : ") (trying NOT to make a emoticon here)



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Ahh, it's a bit of black magic. The toggle only appears once you type in an image name for the main render; if you leave it as 'ip', the option is hidden. Easier to see in this animated gif (click to play):





Still doesn't answer your COP question though, sorry!

Edited by mestela
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wow! that is voodoo magic! I would have been less surprised if you have told me to sacrifice a goat or run around the office naked covered in peanut butter !! :)


But thanks a lot for your reply, it's greatly appreciate!

I'll continue to investigate and see if I can figure it out, otherwise I'll see if I can import the animation and try to render the velocity information to the RGB channel.

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Had a look, seems cops doesn't like that image. I suspect its the channel names, they look a little messed up. Djv also has problems loading the motion layer. Nuke loaded it ok.


In nuke I renamed the layers to mv (as 3 channels, so mv,r, mv.g, mv.b ) , and depth (as depth.z), and wrote out a clean exr. That loads into cops fine.


Attached it if you wanna take a look.



Edited by mestela
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