Käsitesivu

Refers to a system based on projective geometry and used in art, architecture, cartography and other disciplines for representing three-dimensional objects or spaces on a two-dimensional surface by following strict conventions by which imaginary sight lines project from the observer's eye to the object, transmitting an image of the object to an intervening transparent surface, which is the picture plane. The mathematical requirement of a projection is that every point in the object and the corresponding point in the image must lie on a straight line, the projection ray; projection rays typically pass through the center of the projection. In many cases, the center of the projection is assumed to be infinitely distant from the object, so that all projection rays are parallel rather than converging as they recede in space. Although its meaning overlaps somewhat with "perspective," "projection" is used for technical and architectural drawings that emphasize the mathematical properties of objects that are preserved in the images; "perspective" is used for art works and renderings that include the distortions of lengths, angles, shapes, and straightness of lines that optically appear to occur as objects recede into space.

Refers to images cast on a surface or in space by optical means, generally by placing an object between a light source and the surface or a designated point in space. They include images created with slides or film, digital images or other computer files, or shadows cast from opaque objects; projections on surfaces may be cast from the front or the rear of the surface. They also include holograms cast onto a point in space.