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?
Let us take a look at how one of these scholars or critics goes about his work. Let’s say he is going to write a commentary on a particular painting. If he is not a man of intuition, certain features will characterize his approach. First he will try to place the painting genealogically, or he will try to define the painting by assigning it to a particular school. He feels uneasy unless he succeeds in doing this.
But more than anything, he is extremely wordy. He seems incapable of speaking of beauty without innumerable layers of adjectives.
One can study an object and note its features, but that only touches the surface. A knowledge of an artwork’s properties does not lead to an understanding of its essence.