Gembench
A gem-cutter's bench in a stone-walled workshop nook at dusk: turn the rough stone under a warm brass lamp and hold the lap wheel to grind each facet in turn, watching the stone's true colour reveal itself. The materials probe rides in the tray beside it: five display gems share ONE material and get their distinct colour purely from per-instance mesh vertex colour, read by the lab's hand-authored Lab/Foliage shader (URP's own Lit shader reads neither vertex colour nor time, established by the previous piece, millrace) rather than from five separate materials - the first time that shader has carried a small close-range hero prop instead of terrain or foliage. A sixth control gem uses a real per-material colour so the comparison has a known-good baseline.
Concept prompt
A gem-cutter's workshop nook at dusk: a heavy walnut wooden bench holds a rough gemstone mounted on a dop stick over a small motorized lapidary wheel, one articulated brass lamp with a loupe arm casts a tight warm pool of light on the stone, a velvet wine-red tray beside it holds five faceted cut gems in ruby red, sapphire blue, emerald green, citrine gold and amethyst purple that catch the light, brass tweezers and a small scale rest nearby, warm stone wall behind with a small deep-set arched window showing a dusk violet-blue sky fading to an amber horizon over rooftops, dust motes drifting in the lamp beam, high-end stylized 3D game render, no text, no watermark, no UI
