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?
Modernist planning was obsessed with absolute numbers, including the minimum dimensions of rooms, open space per capita, and the one-size-fits-all head counts of neighborhood units. This was often pegged at five to seven thousand and was used as a formula for determining the distribution of schools, shops, sports fields, and other facilities. The failure of such planning is not in its effort to be comprehensive or to equalize access to necessary facilities. It is, rather, the attempt to rationalize choice on the basis of a homogeneous set of subjects, a fixed grammar of opportunities, a remorseless segregation of uses, and a scientistic faith in technical analysis and organization that simply excludes diversity, eccentricity, nonconforming beauty, and choice. The utopian nightmare.