tes_metal

Bare-metal surface shader for the tesla hall's hero metals (toroid, mast electrodes). Shades with the hall's analytic light rig plus a procedural environment — warm floor-bounce / dark-roof gradient, moonlit-window band, roughness-widened high-bay glints — scaled by the analytic EnvBRDF approximation, so the metal reads as metal at night instead of black plastic. Direct light is F0-tinted Blinn lobes from the same rig.

Per-frame drives from p_tesla:

• flash — discharge flash: toroid-side glint/specular boost + silhouette rim backlight.
• glow — corona skin emission (glow_color tinted).

Vertex stage carries part-local position in vertex color; light positions are part-local, matching tes_floor / tes_wall.