Render Object Alpha

[jbashyam]

Is it possible to render the alpha of a certain object in the scene, yet still render the whole scene? I don't mean a holdout where the object you holdout appears as black in the RGB channel, I just mean an alpha channel for that object so that I can color correct it separately in post.

[jbashyam]

Also, how do I render a z-depth pass at 16bits? Right now I'm getting a lot of banding

[Oshyan]

The z-depth (Surface Depth) pass is already 32 bit in EXR.

I'm not sure if you can render out the alpha of a specific object and render the entire scene at the same time. But you could perhaps experiment with the Object Group handling in the Render Layer (Objects tab). Here's documentation on that stuff too: http://www.planetside.co.uk/wiki/index.php?title=Render_Layers_and_Render_Elements

- Oshyan