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?
In System A, there is no architect separate from the contractor. We are builders, simply. As builders, we have a direct feeling about construction. We feel it in our fingers, so it is down to earth. One result of this down-to-earth quality is that everything is somewhat experimental. We make experiments all the time. Sometimes we place a piece of wood this way. Another time, we may like to try it that way. Any time something new comes up in the design of a building, we are very likely to try and invent the best way of building it. This is not a great big invention. Just a simple invention, the way we might invent a way of tying a piece of string, to hold a broken toy together. It is just practical.