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?
I recognize this is a very niche endeavor, but the art and craft of maintaining a homepage, with some of your writing and a page that's about you and whatever else over time, of course always includes addition and deletion, just like a garden — you're snipping the dead blooms. I do this a lot. I'll see something really old on my site, and I go, “you know what, I don't like this anymore,” and I will delete it.
But that's care. Both adding things and deleting things. Basically the sense of looking at something and saying, “is this good? Is this right? Can I make it better? What does this need right now?” Those are all expressions of care. And I think both the relentless abandonment of stuff that doesn't have a billion users by tech companies, and the relentless accretion of garbage on the blockchain, I think they're both kind of the antithesis, honestly, of care.