Referencing a Material in C++

Development Asset Creation
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1

Hi,

I’m trying today to link the material of a mesh inside my C++ to manipulate its properties from here. Unfortunately I can’t get to make it work.

I tried in my header :

		class UMaterialInstanceDynamic* MI; //-> works
		class UMaterialInstance* MI; 		//-> Soft crash the editor, crash the game

Then, in my function I tried :

		float t = 0;
		
		MI = NewObject(); //compile without errors
		MI->Create( Mesh->GetMaterial(0), this ); 	//no effect
		MI->Parent = Mesh->GetMaterial(0); 			//no effect
		
		MI->GetScalarParameterValue(TEXT("blend_mask"), t);
		
		elog(t);

So, the GetScalar function only work (I get my correct value) if I use a Material Instance (but it crash the editor), and if I use a Material Instance Dynamic the GetScalar return me 0.

I’m a bit lost here, while one would works but crash and the other one wouldn’t work at all ?

By the way, why can I edit directly the “Parent” variable and not use the SetParentInternal() function (since it is protected) ? That seems strange, shouldn’t be the inverse ?

2

Since I stuck on this, I tried to see if I could setup my idea with Blueprints. Unfortunately I’m hitting the same problem. How could I convert the MaterialInterface to a MaterialInstanceDynamic ? It seems there is no function that would allow me to cast this or convert it.

material_dynamic.jpg
material_dynamic.jpg839×370 48.8 KB

3

You want to use the factory function UMaterialInstanceDynamic::Create and provide the material you’d like to use as the parent. In Blueprint you’d use a function like CreateMIDFromMaterial or CreateMIDForElement.

The Parent member being a public variable is legacy from UE3 and I’d like to clean that up. It must be changed by calling SetParentInternal and that function is intentionally non-public as it must only be called in-Editor on MICs and may not be called after creation on MIDs.

1 Like
4

I see, thanks. However can you clarify me if the following is the correct way to reference a material ? Because I tried it and it doesn’t return any value from the original material (it stays at 0 while I’m expecting 0.353 as I typed it in the editor).

 MI = NewObject();
MI->Create( Mesh->GetMaterial(0), this );
5

The function is static, so what you actually want is something like this:

UMaterialInstanceDynamic* MI = UMaterialInstanceDynamic::Create(Mesh->GetMaterial(0),this);

Why C++ allows calling static member functions as if they were methods is beyond me :slight_smile:

6

Thanks a lot, I got it working properly now ! :slight_smile: