Every rib, pier and arch soffit occludes what stands behind it, and the ruling turns as each surface curves. The air is the only variable: the nearest bay closes to unbroken black, and the ribs at the far end thin to hairlines on paper. Light enters through the clerestory and crosses the hall as a hard-edged slab of bare paper, specked with dust. Each seed is a different hall: its own bay count, vault profile and eye height.