Texture bake Alpha?

I did a search and couldn’t find anything on this.

Is there a way to bake a material with its transparency? Namely, I need to bake a shine onto something, and have the alpha to show through objects behind it. I keep getting the atmosphere baked in.

Is it not possible?

I’d appreciate an answer to this as well. The docs for 2.49b claim it’s possible, but don’t say how.

It’s possible.
The object that has the texture enable Ztransp and set its alpha to 0 and the plane that receibe the shadow enable Shadow and Trashadow in Shaders section.

http://www.fileden.com/files/2008/7/18/2009564/baked_trashadow.PNG

For cycles what I did was bake 2 times creating 2 textures, 1 the regular bake texture and the other is just a glossy bake type, only the color and that created a B&W image that then you can use as a mask in photoshop…