CGTalk - Help with rendering alpha channel

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dax3d

12-01-2002, 06:49 PM

Hi,

I have tried searching everywhere for the answer, but couldn't find it so far.

I am trying to render out just the alpha channel of an animation in Maya. In the render globals I just checked "alpha channel (mask)" and even checked mask in the output settings of the camera. When I render though, the images is still in full color.

Can anyone tell me what I'm doing wrong?

thanks

mikeS

12-01-2002, 08:07 PM

hi
do you need the alphachannel for compositing?
well when i rendered my last animated short i had to compose several layers .i think not all output settings like avi support alpha channels. you have to switch to tiff or targa to see the alpha channel and to use it
hope i ve helped u

mikeS

rudymassar

12-01-2002, 08:21 PM

I tried to render in passes with everthing unchecked... didn't work. Diffuse, shadow, spec or colorpass only... also no go. I seems that Maya renders the RGB anyhow even with the RGB channels turned of in the RG.

I guess the "workaround" is: you save your file with no light and textures what so ever... to speed up the render process. Also use a black surfaceshader for all the objects in you scene. If transparent turn the spec color to black... if this shader also have a reflectionmap... remove the image.
Hopefully there's somebody out there with THE solution.

Greetz!Rudy Massar
3d-artist.nl (http://3d-artist.nl)

dax3d

12-01-2002, 08:43 PM

Hi,

Yes, I'm trying to use this for compositing in After Effects. I am also trying to render out to a series of targa images for alpha info.

So far I have no lights in the scene, but I do have a shader on there. I am trying to follow a specific tutorial, and it says to have a shader on the object then render out the alpha channel. I'll keep trying

thanks guys

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