pad_snow

Sugar snow. The mesh is a lattice of degenerate quads; each one hashes the world cell it stands in into a grain, moves that grain through its own cell on the film's clock, and billboards it at the camera. Grain identity comes from the world cell rather than from the vertex, so the volume can be snapped along with the camera and the field still reads as standing still in the world.

Travel direction is read off front_x with exactly film.frontAt's falloff: ahead of the nebula front the sugar falls, behind it the sugar rises, and on the line it hangs. One shader serves both the 3 m macro volume of shot 1 and the 1500 m volume that puts sheets of it between the islands in shot 2 — cell, grain, fall_speed, drift and the two fade distances are what differ.