Add Material Slots via Script

Development Pipeline & Plugins Editor Scripting
1

Is there any way to create additional material slots on a StaticMesh asset via python or BP?
Basically I want my lower lods to use different materials but to do that I first need to add material slots.
I’ve searched the docs but failed to find a way myself. Seems you must click the + button in the Static Mesh editor.

2

I would create a master material with all the functionality for your highest detailed LOD. Than I would add parameterized switches in the material to switch off what I don’t need on lower LODs.

Afterwards I would create material instances from the master material with some switches on and some off (how it is needed).

These material instances can than be assigned to the specific LODs.

3

In python I would do something like:

path_to_sm = "/Game/Assets/SM_Test"
sm_obj = unreal.load_asset(path_to_sm)

sm_mats = sm_obj.get_editor_property("static_materials")

new_material = unreal.StaticMaterial()
new_material.material_slot_name = "New Material Slot"

sm_mats.append(new_material)

sm_obj.set_editor_property("static_materials", sm_mats)

Hope this helps!

4

Oh, excellent. This is the kind of thing I was looking for, thanks!
I wonder though…I tried get_editor_property(“static_materials”) and it failed.
This may be because I’m on 4.25 or because I didn’t do load_asset() before.
Thanks again! Will try shortly.

5

You’re right, I just tested it and this solution doesn’t work in 4.25. I’m not sure exactly the best way you’d want to do it, but this might help:

def add_material_slot(sm_path, new_slot_name):
    sm_obj = unreal.load_asset(sm_path)
    
    new_material = unreal.AssetToolsHelpers.get_asset_tools().create_asset(new_slot_name,
                                                                           sm_path.rpartition("/")[0],
                                                                           unreal.MaterialInstanceConstant,
                                                                           unreal.MaterialInstanceConstantFactoryNew())

    sm_obj.add_material(new_material)

There might be a better way that doesn’t involve creating a new material, hope this helps though.