Decal Material and ActorPositionWS

Hello,
I would like to create a decal instantiated when the player hits a wall.

What I want to do is to apply a sphere mask to the opacity of the material. The idea would be to make the sphere mask centered to the Decal Actor world space position.

I tried with the Object Position, but I get an error at compile time:


Error [SM5]  error X3004: undeclared identifier 'GetObjectWorldPosition'

I think it is because a Decal has no object…

So I tried the Actor Position.

But when trying at runtime, it seems the decal material is using the player position as sphere mask center.

Is it normal?

Thanks in advance,
Luca