My ceiling looks dirty – in patches. I built a palace from quartz slabs expecting clean, white walls and ceiling. The walls look good, but the ceiling has patterns of deep shading depending on what's built above the slabs, not what's lighting them from below.

In fact, the lighting below these slabs has very little effect, as if the light must pass through the slab to the top before it can brighten the near face on the underside.

The slab ceiling is at the upper-half of its block level (so the underside is mid-block). The underside seems to be getting its lighting data from the upper side. It should be getting its light data from beneath (i.e. The illumination for an exposed slab top or bottom face should be whatever impinges upon the same face of the full block at its coordinates).

I have done some advanced searching here to find any earlier reports of this lighting bug, but have found none. I found other lighting bugs, but not this one. If you think you see a duplicate, then please PM me before dismissing my report (I'll happily admit duplication if it really is the case).