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?
Placing work and commerce near residences, but buffering it off, in the tradition set by Garden City theory, is fully as matriarchal an arrangement as if the residences were miles away from work and from men. Men are not an abstraction. They are either around, in person, or they are not. Working places and commerce must be mingled right in with residences if men, like the men who work on or near Hudson Street, for example, are to be around city children in daily life—men who are part of normal daily life, as opposed to men who put in an occasional playground appearance while they substitute for women or imitate the occupations of women.