air_shimmer

The heat standing over stone the sun has been on. A low slab of air across the mosaic: a view ray is bent by however much of the slab it crossed and by how close that crossing was to the patch, so a camera lying on the floor and looking down the hall gets a whole room of shimmer, a camera looking straight down gets almost none, and air over stone the sun never reached does not move at all. The displaced read comes from zero::scene_color; the ripple runs on film_t and on nothing else.