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?
Is there positive value to recognizing an invisible Design Concept as a real entity in design conversations? I think so.
First, great designs have conceptual integrity—unity, economy, clarity. They not only work, they delight, as Vitruvius first articulated. We use terms such as elegant, clean, beautiful to talk about bridges, sonatas, circuits, bicycles, computers, and iPhones. Recognizing the Design Concept as an entity helps us to seek its integrity in our own solo designs, to work together for it in team designs, and to teach it to our youth.
Second, talking frequently about the Design Concept as such vastly aids communication within a design team. Unity of concept is the goal; it is achieved only by much conversation.
Thus, moviemakers use storyboards to keep their design conversations focused on the Design Concept, rather than on implementation details.