In optics, a caustic is the envelope of light rays reflected or refracted by a curved surface or object, or the projection of that envelope of rays on another surface. The caustic is a curve or surface to which each of the light rays is tangent, defining a boundary of an envelope of rays as a curve of concentrated light.
A piece of milled plexiglass acting as a projecting lens; via the Computer Graphics and Geometry Lab at the École Polytechnique Fédérale de Lausanne
New milling techniques applied to glass and plexiglass panels could be used to “create windows that are also cryptic projectors, summoning ghostly images from sunlight.”
[Pauly and Bompas] hope that the technique will be used in architectural design, to create windows that mould sunlight and throw images or patterns onto walls or floors,” which, if timed, milled, and manipulated just right, could produce a slowly animated sequence of images being projected by an otherwise empty window during different times of day.
To control the shape of a caustic pattern generated by a specular or refractive surface, we need to solve the inverse problem: how can we change the surface geometry, such that incident light is redirected to produce a desired caustic image?
And through their unremitting efforts they were able to acquire once again the knowledge and feeling that qualified them to return as full-fledged members of society...
Time passed with shocking swiftness, and soon the boy was thirty-two, the girl thirty.
One beautiful April morning, in search of a cup of coffee to start the day, the boy was walking from west to east, while the girl, intending to send a special-delivery letter, was walking from east to west, both along the same narrow street in the Harajuku neighborhood of Tokyo. They passed each other in the very center of the street. The faintest gleam of their lost memories glimmered for the briefest moment in their hearts. Each felt a rumbling in the chest. And they knew:
She is the 100% perfect girl for me.
He is the 100% perfect boy for me.
But the glow of their memories was far too weak, and their thoughts no longer had the clarity of fourteen years earlier. Without a word, they passed each other, disappearing into the crowd. Forever.