You only need "texture_palette.py" file from this repository and nothing else. README.md and LICENSE.md are provided for github and convenience only.
This project is under MIT license.
There's a short youtube video demo you can watch here:
This is a simple tool for generating multi-material meshes for game engines, using low-polygonal style.
The main idea is that in any material you can define multiple 'sub-materials', and then based on the sub-material configuration, the script will generate a combined 'palette' texture, that will store albedo color, metallic and roughness, and emission, along with emission power.
The reason why this exists is because FBX exporters do not correctly transfer PBR data into game engines, and usually it has to be typed in by hand. This is not much of a problem in a traditional workflow, where everything is painted on a texture, but it is a pain to deal with when you have a model with LARGE number of simple untextured materails. Also, having multiple materials increases number of drawcalls, which is something you'd want to avoid.
To use the tool, create any blank material, unfold "Multitexture" panel, click "Build Material". This will create node network, all the required textures, and it will also connect them correctly to each other.
You can destroy all the nodes if you want, just click "build" again, and it will regenerate the shader. You update the texture by pressing the same button. The textures will not be rebuilt automatically.
To start adding materials, click "add sub material" button. This will create a new sub material where you can configure individual parameters. You can remove it with "remove", move up/down in the list, and so on.
"Assign" and "select" buttons work in mesh edit mode pretty much the same way normal material list does. If you have UV generated, pressing "Assign" will stuff existing UVs (for selected faces) in question into related square, OR reassign it into a new square. This will properly scale down the UVs the first time you do it, so you can just pretty much "Unwrap" and then "Assign", which should work fairly quickly.
Select will select all faces that fit into a specific material square for that particular material.
"Num Column" and "Num Rows" specify how many rows and columns are in the texture, which affects how many materials are stuffed into it. Be aware, that if you change those UVs will NOT be recalculated and you'll have to redo all of them. "Cell size" is size of a single square in pixels.
Now, "max emission" affects a multiplier you apply to emissive color. The idea is to store emission color in RGB, and multiplier in alpha channel, where ALPHA 1.0 will mean the maximum emission power. This is something that you'll need to replicate in the game engine, and won't work out of the box. If you don't need emission overbrightening, just leave it at 1.
"Generated texture formats."
"Albedo" texture stores albedo in RGB, and Alpha in alpha channel.
Metallic texture stores Metallic in RG channels, and Roughness in BA channel.
Emissive texture stores emission color in RGB and emission power in alpha.
Value stored in alpha channel is based on emission strength and max emission.
I've added one more revision. Now it is possible to combine multiple materials used by different meshes into one multi material. To do that, select the meshes you want to process, and then choose "Combine Mesh Materials" from "object" menu (can also be reached via search). If nothing is selected, all objects in the scene will be processed. This will make copies of existing meshes, replace materials (on those copies) with a single "combined material", build that material and then select the new objects. The process will skip meshes that already have multitexture enabled.
And that should be all. Have fun.