In certain conditions, the white walls at home take on the character of a light box. In traditional Japanese architecture the intensity of atmosphere has a lot to do with the way natural light is filtered through the shoji paper panels, suffusing the interior spaces with subdued light, calming the spirit and sharpening the senses.
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?
Picture a blind man probing his way with a cane. While he is alert to the feelings in the hand holding the cane, the crucial distinction may be defined by saying that these feelings are not watched in themselves, but that he watches something else by way of them, that is, by keeping aware of them. He has a subsidiary awareness of the feelings in his hand, feelings which are merged into a focal awareness at the end of the cane, constituting two kinds of awareness that are mutually exclusive — "from awareness" and "focal awareness".
There is here a particularly interesting phenomenal transformation. The sensations of the cane on his hand (the surface of the cane as it touches the palm of his hand, etc.) are lost. Instead, he feels the end of the cane as it touches an object...If our blind man shifts his attention from the tip of his cane to his hand, the meaning on the end of the cane disappears.