baking to multiple objects at once with multiple materials I'm learning Blender because I want to be able to make simple assets for my Unity3D projects. For example, let's say I want to design a simple level (labyrinth-like) but with some premade lamps and different tiles on the floor. So i have a few objects in the scene, each with a different material. 

I'm a total newbie when it comes to baking. I guess, that what I need is a combined bake. I know how to bake a simple single object with one material: I need to unwrap it, create an image texture in the node editor, set it to a new image and then click "bake". 

But when I want to bake this whole "level" that I want to be a single object in the game (so I'll need to export it in OBJ or sth similar), what should I do? Should I Ctrl+J all the things to merge them into one object and then unwrap it and do the usual stuff? Won't it mess up my materials?
Use the 'Texture Atlas' addon. It comes with Blender 2.7 or higher and can be enabled in the preference panel.

Once enabled, you can access it from the Render Panel: