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?
“Controlled environments” are another of modernism’s great obsessions. Extravagant amounts of energy are spent to keep buildings—as well as skyway systems, shopping malls, and domed stadia—at a constant temperature year-round via entirely mechanical means. The folly is not simply a touchy-feely isolation from the authenticities of nature, which can admittedly be cruel, but a larger disciplinary presumption that seeks to extend the centralized authority (central air, central government) of power ever more comprehensively. It is possible that this particular hubris may have pushed Gaia to the tipping point.