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?
Back before COVID-19 hit the global scene, I thought it would be pleasant to have a list of the good things in life. This list wouldn’t be an exhaustive account of all the checked boxes on Maslow’s Hierarchy of Needs, but rather would document small pleasures which evoke some kind of clear and specific emotional response. If I had The Sads, I could pull up this list and sink down into the sensory details of, say, that strong hit of pine scent you randomly get on a hiking trail.
Now that we’re all in the thick of this pandemic, this new tiny side project—Good Things—has offered me a peaceful little portal to things I miss. Your mileage may vary, but I’ve found that reading my personal list of good things can be comforting as I help protect my community by sheltering in place.