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?
Now, I understand deadlines. I understand that the plane will take off whether or not I’m on it, or the importance of beating the holiday retail rush, or that "the show must go on". It is perfectly clear to me how people use timekeeping technology to coordinate social activity. It’s actually quite remarkable when you step back and look at it. But, over the years, I have observed that there is a difference between those examples and the ones around the delivery of Things, which tend to be completely arbitrary. When you wrap an arbitrarily complex endeavor up in a neat launch date, the goal seems to be more about coercing the people beneath you to absorb the overhead of all the details you left out—that or sweating it yourself. As a tool for coordinating human activity, I have come to believe that the Thing-deadline calculus is, considering more sophisticated alternatives, unnecessarily crude.