I were doing some test renders using Superfly and had/have some problems with noise or artifacts in the renders, which are pretty annoying :) However I started doing some testing, as it at least to me seems that there are some weird issues with the PhysicalSurface node when it comes to roughness. So i made a test scene with a Box and a tile material linked to the metallic and roughness with one tile being black and the other white. In front of the box is a single point light with ray trace shadows. The material look like this:

First render:

Looks to be correct the light gets reflected in the tile but not the one underneath.

As the light is moved down so it around the edge between the two tiles, noise or artifacts starts to appear around the edge.

As the light is "behind" the non reflecting tile, its clear that some noise appear where the point light is.

So i tried to increase the roughness from 0.1 to 1, which had little effect.

Next i raised the pixel samples to 40, to see if that could fix it, (Took around 10-15 minute to render) But did nothing to remove it.

So I tried to unlink the tile map from the roughness and just use the same roughness for the whole object.

This seems pretty weird to me, that the hotspot of the light reflects where it shouldn't and it looses intensity as it gets close to edge of the reflective tiles where it then regain its intensity as it is reflected.

To me something seems to be wrong, especially the white noise that is created and even with 40 pixel samples its still there. If this were an actual scene with reflective objects scattered around. The amount of noise could be quite a lot with practical, as i see it, no way to fix it.

Does anyone have an idea whats going on here or whether its a bug or if im missing something?