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?
It seems this transformation, from physical object to vector of data, is a general and oft-repeated process in the history of technology, where new inventions begin in an early experimental phase in which they are treated and behave as singular individual things, but then evolve into vectors in a diffuse and regimented system as the technology advances and becomes standardized.
In the early history of aviation, airplanes were just airplanes, and each time a plane landed or crashed was a singular event. Today, I am told by airline-industry insiders, if you are a billionaire interested in starting your own airline, it is far easier to procure leases for actual physical airplanes, than it is to obtain approval for a new flight route. Making the individual thing fly is not a problem; inserting it into the system of flight, getting its data relayed to the ATC towers and to flightaware.com, is.