Setting Static Switch parameters of a Material Instance in Python

Development Pipeline & Plugins Editor Scripting
1

Hi all,

Documentation at unreal.MaterialEditingLibrary — Unreal Python 5.1 (Experimental) documentation shows that we can get the material static switch parameters through get_material_default_static_switch_parameter_value(material, parameter_name). There are set methods for scalar, texture and vector paramters, but not for static switches. Can anyone please help me with a way to set static switch paramater values?

Thanks

2

I am wondering the same thing. Did you find any workaround?

3

Same here…

4

Tried setting them using the set scalar? Working in angelscript and that seem to be what I’ve used.

5

Didn’t manage to do it using scalar. Anyone knows a way to achieve this?

6

A workaround is to create material instances variants with these static parameters turned on/off and select those instead of settings the parameters via script

7

same problem here, really annoying.

8

still not possible on 4.27
really annoying.

9

There is no pure python way to solve it.
I develope a C++ BlueprintLibrary which can solve this problem.

C++ code I reference from a Japanese blog

And I found some issue with this code, So I write a modified version of this function.

here is my blog article, sorry but in chinese.
C++ Solution below

void URedArtToolkitBPLibrary::SetMaterialInstanceStaticSwitchParameterValue(UMaterialInstance *Instance, FName ParameterName, bool SwitchValue, bool bOverride)
{
    TArray<FGuid> Guids;
    TArray<FMaterialParameterInfo> OutParameterInfo;
    Instance->GetAllStaticSwitchParameterInfo(OutParameterInfo, Guids);
    FStaticParameterSet StaticParameters = Instance->GetStaticParameters();

    for (int32 ParameterIdx = 0; ParameterIdx < OutParameterInfo.Num(); ParameterIdx++)
    {
        const FMaterialParameterInfo &ParameterInfo = OutParameterInfo[ParameterIdx];
        const FGuid ExpressionId = Guids[ParameterIdx];
        if (ParameterInfo.Name == ParameterName)
        {
            FStaticSwitchParameter *NewParameter =
                new (StaticParameters.StaticSwitchParameters) FStaticSwitchParameter(ParameterInfo, SwitchValue, bOverride, ExpressionId);
            break;
        }
    }
    Instance->UpdateStaticPermutation(StaticParameters);
}

For the real world example, you can check my C++ Plugin Unreal-PyToolkit.

After add and compile Unreal-PyToolkit plugin into your project
you can use it with python below

import unreal
py_lib = unreal.PyToolkitBPLibrary
material = unreal.load_asset("material_path")
py_lib.set_material_instance_static_switch_parameter_value(material,"param",True)
10

bump, that rally needs a fix. not possible in 5.0 also

12

Found workaround. Use LERP function and pass it scalar hard 0 or 1, then you can use set scalar from python. Would work for something like replacement to “isMetallic?” bool or “isAlpha?”. Might not be suitable for all applications tho.
Original: controlling a StaticSwitch with a Float/Scalar/Constant 1 in a Material - #2 by Lovecraft_K