Baking the multiple materials of an object into a single one

SWTOR's models typically use multiple materials: one or two per character object (a head with skin and eye materials, a piece of armor revealing skin…), or even dozens of those in environmental stuff such as spaceship interiors.

Sometimes, the apps we want to export a SWTOR model to require that the models have a single mesh, single UV map, and single material with one texturemap per channel (one diffuse, one glossy, one normal map, etc.). Just joining the objects into a single mesh (ctrl-j) doesn't merge the materials into a single one, so, baking won't solve that…

…Without a little bit of extra fiddling. Here there are a couple of YouTube videotutorials showing how to set up bakes from multiple materials to create single, encompassing ones.

• This one is maybe the simplest, most direct guide:
  Baking to a single Material from many Materials in Blender, by Average Godot Enjoyer

• This one is more detailed, and points out a few things to avoid overlaps and quality issues):
  Bake Multiple Materials/Objects to One Texture Map, by Ryan King Art

Basically, the technique consists of:

1. Joining the objects into a single mesh object.
2. Setting a new blank UV Map, selecting it, and using Blender's unwrapping tool to auto-UV the object to that map.
3. Adding to all the materials in the object texturemap nodes using the same target image and that new UV Map (via copypasting from one material to another), taking care of leaving them unconnected and "active" (last or only selected one).
4. And baking the channels we need (diffuse, normals, opacity, etc.): each channel's results will accumulate into the single image we specify in all the target nodes

While we don't have a proper automation for this just yet, we ought to be able to add a couple of conveniences, such as a one-press-button to add target nodes and make all target nodes "active", set image size, etc. to our tools. No promises 🙂.