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?
Normally after the design was built, you would find places for the art to be located and then you would go out and select the artist that you wanted. That is historically, the traditional way to go.
But this time, someone else was calling the shots. A planning official, basically, who comes along and says, “We want you guys to work with an artist.” And the architects are like, “Sure of course.” But then the official goes—“No, you don’t quite understand. We want you to use an artist as a co-equal member of the design team.” That is, the artists are going to have just as much control as the architects. It was really unheard of.