Blender Mesh has duplicated materials

Question

I have a huge problem. I’m a game developer and currently trying to create a level with Lego buildings. So I export them as zmbx from mecabricks and import them to blender, combine the meshes (joined them into one) and then export it as fbx which I than can import into ue5. The problem is that the mesh has to many materials and nanite can’t handle a mesh with over 64 material slots (mine, a simple building, has around 650), each brick has a material, which is totally unnecessary cause the most of these materials have the same color/texture. They are called like „mb:o:234:199“, when the last number is the same (199) all these materials have the same color/texture.

And then for example other materials with the ending 134 are also the same … I saw that a lot of guys found a way to combine all materials into one. I tried some blender addons like creating an atlas, but for that you have to create a new uv map which my pc can’t handle because of the mesh (Rtx 3070ti ox, ryzen 7 5800x, 32gb Ram). And then I get a weird texture and the mesh is completely filled with random colors. I’m new to blender so I have no other ideas. Please help

Answer 1

Before exporting, creating atlases, uv maps and so on you could reduce the amount of materials to only the necessary ones. Go over to the Scripting workspace and create a new .py file with the following script. Select your object in object mode and run the script:

import bpy

context = bpy.context
obj = context.object
mesh = obj.data


suffixes = [':199', ':44']  # add more suffixes

for suffix in suffixes: 
    mat_slots = obj.material_slots

    basemat = None
    basemat_index = -1

    for index, slot in enumerate(mat_slots):
        mat = slot.material
        if mat and mat.name.endswith(suffix):
            basemat = mat
            basemat_index = index
            break


    if basemat:
        for face in mesh.polygons:

            slot = mat_slots[face.material_index]
            mat = slot.material
            if mat and mat.name.endswith(suffix) and mat.name != basemat.name:
                    face.material_index = basemat_index

        for i in range(len(mat_slots) - 1, basemat_index, -1):

            mat = mat_slots[i].material
            if mat and mat.name.endswith(suffix) and mat.name != basemat.name:

                obj.active_material_index = i
                bpy.ops.object.material_slot_remove()

This will assign the first found material with suffix :199 to all faces which have another material (not the first found) with suffix :199 and remove these material variations afterwards.

Edit: updated script to process multiple suffixes

Then it will process the next suffix (:44) and so on.