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?
Even with all the features and plugins, Canvas presumes certain ways of organizing classes that might not be universal, just typical. And if (like me) you’re an atypical user, you have to choose between constantly fighting with the system or gradually doing more and more things the way Canvas wants you to do them. This, by the way, is why it’s never true to say that technologies are neutral and what matters is how you use them: every technology without exception has affordances, certain actions that it makes easy, and other actions that it makes difficult or impossible. A technology whose affordances run contrary to your convictions can rob you of your independence — and any technology deployed on the scale of Canvas will inevitably do that. It will turn every teacher into an obedient Canvas-user. I don’t want to be an obedient Canvas-user.