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?
Dame Wendy Hall, at the University of Southhampton, sought to extend the life of the link further in her own program, Microcosm. Each link made by the user was stored in a linkbase, a database apart from the main text specifically designed to store metadata about connections. In Microcosm, links could never die, never rot away. If their connection was severed they could point elsewhere since links weren’t directly tied to text. You could even write a bit of text alongside links, expanding a bit on why the link was important, or add to a document separate layers of links, one, for instance, a tailored set of carefully curated references for experts on a given topic, the other a more laid back set of links for the casual audience.