I've been doing some research on deffered decals recently and also learning how to use them along the way. One thing that I still haven't grasped is how much you should use before performance starts tanking. From what I understand, a Decal Actor uses only one material and costs one draw call. Moreover, the documentation…
They can get pretty expensive, pretty fast but it really depends on how you're using decals, how big the bounding boxes are, what they effect and the biggest factor is how complex the shaders are. I think if they overlap, they can be more costly also. I believe it causes any mesh that is hit by a decal to be rendered…