I'm preparing to re-model a Table Mat (like a Tatami Mat) tomorrow. I will need to do some baking from geometry onto a plane-texture. I know how to do that, except I don't know how to bake the alpha? I don't see alpha in the list of what I can bake in Cycles. There is transmission, but I think it's not the same. Is there a way to bake alpha? I'm pretty sure I will need it to compose materials in the Compositor. Would it help if I set world color to transparent in the Film tab in the Render properties? Will it then bake with transparent alpha?
5 Answers
I don't think it's possible to bake alpha directly, but you can try making a new shader mixing a white and a black emit shader together using the alpha of your textures as mask, then bake that into a new texture.
It will be a bit tedious if your scene is too complex, but I don't know of any other way. If you have too many objects it's probably a good idea to try to automate that using python.
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...
leave your alpha node plugged in, and bake with combine to your texture. Than alpha output works from your base color texture image.
I'm not sure what you need but I believe you should be fine just baking the textures and use it as diffuse while using another texture with alpha information on the same material to provide the transparent areas.