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?
Scale refers to how we perceive the size of an element or space relative to other forms around it. All things – a tea cup, a building, language, entire eco-systems – consist of smaller components. It is the relationship of the smaller elements which determines the character and degree of life of the whole.
Objects which contain a high degree of life tend to contain a beautiful range of scales within, which exist at a series of well-marked intervals and have clearly recognizable jumps between them. To have good levels of scale, it is extremely important that the jumps between different scales of centers not be too great or too small.