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

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.