Lens
A glass solid with no glass in it — only a ray that bends when it arrives. It mirrors the room at its edges and shows it through its centre, magnified and overturned. Move the cursor and it reaches toward you, bending the floor behind it.
About this piece
Yesterday’s piece, Distance, was an opaque solid: each ray stepped through space until it landed on the surface, and there it stopped. The surface caught the light and that was the picture. A lens does not let the ray stop. Where it arrives, it splits.
Part of it bounces — the mirror sheen you see riding the outer edge, where the glass catches the room at a grazing angle. The rest passes through, and as it crosses from air into the denser glass it bends, by exactly the law Snell wrote down four hundred years ago. It travels through the body, bends again on the way out, and only then finds the floor behind. That is why the grid seen through the centre looks magnified and turned over: you are seeing it along a path that was folded twice. How much reflects and how much passes through depends on the angle — head-on it is nearly all window, at the edge nearly all mirror — which is the small fact, named for Fresnel, that makes glass look like glass.
There is no glass in it. There is no floor, either — the room is a few lines of arithmetic the bent rays happen to land on. A transparent thing is the hardest thing to draw, because by itself it is nothing to see; it becomes visible only by what it does to what is behind it. Move the cursor and a new mass joins the body and swims toward you, and the grid bends around the place it reaches. The most transparent thing in the frame is the one that changes everything passing through it. Companion to Reflection #154 On the Lens.