Is there an option in Blender to set "background" areas of a normal map bake to have an alpha of 0?
What I am doing exactly, for my own reasons, is baking the orthographic normals of various objects onto a plane in front of them, like this:
But I want everything except the object itself to be transparent in the normal map texture that is baked.
I am using a Python script to also bake maps for objects at every different combination of rotation, generating thousands of files like so:
So any solution or workaround for my particular case has to be scalable. If there is some option or feature in blender to render the empty space around objects onto the normal map with an alpha of 0, finding that is the main goal for me.
I've considered a workaround like rendering a mask with the object silhouette white against a black background and manually multiplying that with the alpha channel of the normal map in Python before saving, but if there's an option I can turn on to avoid the work of writing that script, it would help - doing that would also add to the render time, which is already quite significant, so if I can go a more direct route I would put that ahead of a workaround like that. I'm still fairly new to Blender. Thanks!