Object(s) with multiple surface materials sharing one single texture set.

[Silas Merlin]

To me this was impossible to achieve in 3d-Coat alone until recently with the addition of a checkbox in the beta tools section of preferences : "Treat retopo groups as objects", which is ticked by default, and needs to be unticked for the following to work.
Unchecking "Treat materials as separate textures" simply had no effect, whatever the initial conditions of materials. (If you know what it did and how to make it work, please let me known since the beta tools will eventually be disabled in 4.9).
 

Anyway, here are the steps :

1. Edit > Preferences
-Untick "Treat retopo groups as objects"


2. Separate your retopo object into two or more layers (retopo objects), one per desired surface material
(Use the select tool with faces selection mode, in combination with the buttons at the bottom of the retopo objects panel)
 

3. If you have only one object, just start baking and go to 5.
If you have several object to bake, do this :
-Select tool
-select mode : faces
-double click on object


4.
-In  Bake menu, tick "Bake selected only"
--then, "Bake with normal map"


5.
-In the baking options, untick "Treat materials as separate textures"
You will instantly see the list of surface materials at bottom collapse into one.

-

That's it : In paint room the retopo objects containing the selected geometry will be combined into a single paint object, with one corresponding texture, but several surface materials !

If you have additional objects to bake, go back to the retopo room and select the next object.
 

Edited March 11, 2021 by Silas Merlin