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?
Rain chains are a beautiful and functional alternative to traditional, closed gutter downspouts. Guiding rain water visibly down chains or cups from the roof to the ground, rain chains transform a plain gutter downspout into a pleasing water feature. From the soft tinkling of individual droplets to the soothing rush of white water, they are a treat to listen to.
Rain chains (‘kusari doi’ in Japanese) in concept are not a new idea. For hundreds of years, the Japanese have used the roof of their homes to collect water, transporting it downward with chains and finally depositing the rain water into large barrels for household water usage. Japanese temples often incorporate quite ornate and large rain chains into their design.