cinder_basalt

Crusted volcanic basalt for the mountain's flanks and crater walls. Procedural and triplanar, so it carries detail at any distance on unwrapped terrain: a macro mottle of ash deposits on the shallow slopes, a mid-scale blocky crust, a fine grain that only resolves when you stand on it, and a ridged crack network cut through all of it. The cracks light up as the surface approaches glow_y (the lava lake's height) and inside vent_radius of the crater, so the ground itself reports how close the eruption has come.

Exposes surface(), so capture { pass = "albedo" | "roughness" | "normal" } reads the material rather than the lit image.