Minecraft wiki entry for Light, associated text: In Java Edition, when calculating lighting, the shapes of some blocks are detected: piston, daylight detectors, enchanting table, farmland, lectern, stonecutter, grass path, snow, end portal frame, slabs, and stairs. They have directional opacity, so that the light passing through them can spread only in specific directions. For example, the grass path prevents the light from propagating downward, but the light can propagate in other directions.