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?
Throughout his career, Wilson often answered fan mail and outside requests for his time with this form postcard:
Edmund Wilson regrets that it is impossible for him to: Read manuscripts, write books and articles to order, write forewords or introductions, make statements for publicity purposes, do any kind of editorial work, judge literary contests, give interviews, conduct educational courses, deliver lectures, give talks or make speeches, broadcast or appear on television, take part in writers' congresses, answer questionnaires, contribute to or take part in symposiums or 'panels' of any kind, contribute manuscripts for sales, donate copies of his books to libraries, autograph books for strangers, allow his name to be used on letterheads, supply personal information about himself, supply photographs of himself, supply opinions on literary or other subjects.