Baking Transparent Objects?

Well, I learned the hard way, that I cannot bake transparent objects, like glass or ice, in Cycles (per BE thread from Oct 2014). I get the usual black or white opaque texture map (when using invert).

Anyways, I’ve seen traces that this was possible in Blender Internal. Can anyone explain what I need to know to bake such maps, and what type of map would it be; would it just be an alpha map?

I’m wanting to preserve my glass/ice materials when importing into other applications like Unity.

Isn’t baking the antithesis of transparent objects (especially refractive ones).

Baking by it’s very nature bakes, light, colour, complex mesh data from the current scene into the texture - thereby allowing you to apply this detail as a texture map and hence avoiding having to do it in the application the baked texture is used in.

Transparency on the other hand requires dynamic calculations regarding what is going on in the scene at any given point and so cannot be ‘baked in’.

I believe you can bake some transparency in - in the form of an alpha map - but this will be very basic transparency and will not include refractive contributions like you get in glass and ice.

Thank you for the explanation. I was a bit confused as to how that worked. So the direct/indirect is probably what I would be baking (the effects), and then creating an alpha map for the transparency. Which even then I would lose the IOR. Oh well, good to know.