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?
Some time ago, a friend insisted that people should not listen to practicing architects or read what they write. According to him, the lack of logic in our discourse, the incongruity of our words, and the overzealousness in readings brought about by the biographical revision of our work were of little value.
In his book The Eyes of the Skin, Juhani Pallasmaa approaches it from the opposite direction, but ultimately gives the same advice:
The verbal statements of artists and architects should not usually be taken at their face value, as they often merely represent a conscious surface rationalization, or defense, that may well be in sharp contradiction to the deeper unconscious intentions giving the work its very life force.