col_brick

Running-bond brick masonry for the collapse building's wall chunks. The vertex stage passes object-local position through vertex color so the pattern stays glued to a chunk while it tumbles; the fragment stage derives the local face normal from screen-space derivatives and projects the brick lattice on the dominant local axis. Per-brick hash variation (hue, value, occasional dark clinker), recessed mortar with contact AO, edge chipping keyed off the authored box UVs, weather streaks, dust on upward faces, and a warm bounce term (impact_glow) the part pulses at each strike.