preseed/surfacing.module — give every prop a real surface. The demo's parts author their props as PBR materials with a base colour, a roughness and a metallic and NOTHING ELSE. One flat value across a whole object is what makes an otherwise well-built scene read as untextured blocks: a handrail, a drum and a crate all catch the light identically, so nothing in the frame has a surface. This pass hands each of them real maps. WHAT IT BINDS, AND WHY NOT ALWAYS COLOUR. * normal — the one doing most of the work. It is what makes a flat panel catch a moving light unevenly, which is the whole difference between "lit" and "shaded". * roughness/metallic — the map that matters most on metal, because it varies the specular across the surface. Without it a metal panel is one uniform sheen, which reads as plastic however good the colour is. The PBR shader wants the pair PACKED into one texture (G roughness, B metallic); `<set>_RoughMetal` is that packed pair. * colour — only on surfaces whose authored colour is NEUTRAL or already matches the set. `base_color` MULTIPLIES the colour map, so putting a rust photo under a painted red drum gives a muddy red-brown rather than a painted drum. Coloured props keep their paint and take relief only. Emissive materials are skipped outright. The lamps, beacons, LEDs and arc flares ARE the light in these scenes: a colour map tints the glow, and a roughness map means nothing on a surface that emits rather than reflects. The maps are CC0 sets from ambientCG, uploaded under `/zero/source/textures/ambientcg/`.