Postprocess Material can manipulate the scene buffers


It should be possible to create an Postprocess Material that runs before the lighting with full write access to the scene buffers. So the PP can add effects like wetness or snow without adding this effects to all materials.
I think this feature can be useful for other effects too.

That’s basically what a deferred decal is. But due to hardware / graphics API limitations, full write access to GBuffers are not possible, which is why we have a few decal blend mode options.

I can write to the GBuffer in Decals but I cannot read from it like in a PP. I need the Normal, Base Color and Roughness to calculate the behaviour of the effects.
It seems that I have to do the effects in all Materials but I think the Performance is bad then.