Bismuth Crystal Lab simulates the unique geometry of bismuth crystals — one of the most visually striking minerals in nature. Bismuth forms distinctive hopper crystals: hollow, staircase-like structures where edges grow faster than faces, creating concentric rectangular terraces with geometric precision.
The shader renders these terraced crystal structures using signed distance functions for the nested rectangular frames. Each terrace step is shaded with thin-film interference coloring that mimics the oxide tarnish layer formed on real bismuth crystals when they cool in air. The oxide layer thickness varies across faces, producing the characteristic rainbow iridescence from violet through blue, green, gold, and magenta.
Interactive parameters control crystal scale, terrace depth, oxide layer thickness variation, and viewing angle. The metallic base reflectance combined with the thin-film interference creates the distinctive rainbow staircase appearance that makes bismuth crystals so photogenic.