I'm trying to export a scene to composite in Nuke. When I "render current frame" and save the image from there, I get an image with an alpha channel, but when I batch render the images don't have the alpha channel.

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  • Hard to say. In general your beauty pass should contain the alpha. Bmp is very limited, try to render as exr. Also check if Pass Custom Alpha Channel checkbox is enabled.
    – p2or
    Jul 2, 2015 at 10:33

1 Answer 1


I solved my own problem after some more trial and error. For awhile it looked like the fact that I was using Mental Ray shaders combined with general shaders was the problem, but that didn't really make sense so I kept tweaking. It turns out that an image plane I had tied to my camera was the problem. The image on the plane never rendered out, so I assumed the plane wasn't affecting the rendering, but it turns out it was showing up as a black plane when rendered. I deleted the plane for my render and it works fine now.

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