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?
Handmade washi (traditional Japanese paper) is replete with appeal. Looking at it, touching it, fills me with an indescribable sense of satisfaction. The more beautiful it is, however, the more difficult it is to put to use. Only a master of calligraphy could possibly add to its beauty; it is exquisite just as it is. This is wonderfully strange, for it is merely a simple material. Yet plain and undecorated as it is, it is alive with nuanced beauty. Good washi makes possible our most ambitious creative dreams.
One can gain a glimpse of the quality of a people’s life by the kind of paper they use for writing letters, for literary works, and for various other tasks. Paper should not be deprecated. To do so is to deprecate beauty itself.