# pan_surface Every hard surface on the salt flat, from one shader: the crust, the pan under and beyond it, the runway and apron concrete, the painted markings, the hangar's corrugated sheet, the marker posts and the tie-down rings. It declares **no texture slots**. Every pattern is a function of `input.world_position`, so the material's texture budget and group 0's sampled textures are untouched, and there is nothing here for a texture pipeline to get wrong. ## What `mode` selects | `mode` | Lattice | Used by | |---|---|---| | 0 | jittered voronoi over world XZ, at two plate sizes, plus salt glint | `gs_pan_crust`, `gs_pan_ground` | | 1 | rectangular slab grid over world XZ, plus aggregate | `gs_pan_concrete`, `gs_pan_apron`, `gs_pan_paint` | | 2 | corrugated sheet — ribs, panel seams, run-down streaks | `gs_pan_hangar` | | 3 | painted — grain and macro mottle only | `gs_pan_marker`, `gs_pan_ring` | ## The three things worth knowing before changing it **`wetness` is the film's arc, and it is written every frame.** It runs 0..1 and carries every mode from its dry colour and roughness to its wet ones, with the CRACKS reaching wet first — water stands in the low ground before it stands on the plates. The pan slice writes it from `Film`; nothing else should. **Detail fades on the SCREEN-SPACE FOOTPRINT, not on distance.** `fw` is how many metres of surface one pixel covers, from the derivative of the world position. A camera 28 cm above a ground plane sees it at 8 m under an angle where one pixel spans metres, and any pattern finer than that becomes moire — which is exactly what the salt grain did while looking correct at 1 m and again at 40 m. This film also cuts between a 16-degree and a 78-degree lens, so no hand-tuned distance would hold across both. Every octave, the glint and the corrugation each gate on `fw` against their own feature size, and the `*_fade` properties are a second, author-facing ceiling on top. **The hashes are integer bit-mixes, not `fract(sin(dot(...)))`.** The pan is 7.2 km across and the finest layer divides a metre into sixty, so a cell index runs to a few hundred thousand. At that magnitude a sine-of-dot-product is quantised by f32 into a regular lattice, and the grain came out as a diagonal corduroy weave over the whole near field. A bit-mix over the integer cell index is exact everywhere in this world. Seed offsets are therefore WHOLE numbers of cells — a fractional one names the cell the hash already answered for.