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?
The inglenook, the gazebo, and the porch swing also have strong definitions of their spaces. They are each a bit like a little house set off for a special thermal purpose. They might be termed "thermal aediculae". Although the term aedicula is most often used in conjunction with a sacred or ceremonial little house, it can also be used to describe any diminutive structure used to mark a place as special.
Summerson contends that there is a basic human "fascination of the minitature shelter." Perhaps this is because the aedicula intensifies ones experience of the place by working someone like a caricature. By reducing some things in scale, it exaggerates the importance of other things, most especially the size of a person in relation to the space.