Kit,
I've noticed the same issue with flooring in different rooms rendering shiny in one space and darker/different in another. It actually appears to be true for any large object (long walls, ceilings, etc.). Further, as your screen shot shows, the differences always appear at room boundaries.
Slight but relevant tangent - for a fireplace chimney, I used a soffit extending from the mantel through the ceiling and roof to form the chimney. Whenever I when to PBR, the fireplace above the mantel was blown-out white - like it was being blasted with sunlight - while the lower part rendered correctly for an interior. When I separated the soffit chimney into two pieces - an interior portion and an exterior one - the rendering problem resolved.
A light clicked.
I strongly suspect that the rendering engine lights an object from only one point on that object - and applies that light map to the entire object regardless of whether the lighting changes over the span of that object. I've been watching for this result in my renderings and it seems to be consistently true.
Back to the floors - if my suspicion is correct, the engine is lighting the floors in your dining room using a bright spot in the bay window and lighting the left-hand room using a more shaded spot by the door. Those two light maps are then applied to the entire floor in their respective rooms, with the result you've posted above. Ideally, the engine should be rendering the entire scene using ray-tracing, which would properly light each element on the floors. The next option is that the engine should be ignoring room boundaries when rendering a scene so that all the floors are treated similarly.
I think the milky bits are the engine's attempt at rendering glare. May be wrong here.
Bottom line is I think this is an engine problem and not one we can fix through tweaks.
Kai.
