2D computer graphics: Difference between revisions

Revision as of 23:45, 7 March 2004

Revision as of 00:19, 8 March 2004

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[[de:2D-Computergrafik]]

'''2D computer graphics''' refers to the generation of [[digital imagesimage]]s with the aid of [[digital]] [[Computer|computers]] -- mostly from two-dimensional models (such as [[2D geometric models]], text, and [[digital images]]) and by techniques specific to them. The word may stand for the branch of [[computer science]] that covers such techniques, or for the models themselves.

2D computer graphics are mostly used in applications that were originally developed upon traditional [[printing]] and [[drawing]] technologies, such as [[digital typography]], [[cartography]], [[drafting|technical drafting]], [[package design]], etc.. In those applications, the two-dimensional [[image]] is not just a representation of a real-world object, but an independent artifact with added semantic value; two-dimensional models are therefore preferred, because they give more direct control of the image than [[3D computer graphics]] (whose "user model" is more akin to [[photography]] than to [[typography]]).

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The models used in 2D computer graphics usually do not provide for three-dimensional shapes, or three-dimensional optical phenomena such as lighting, [[shadow]]s, [[reflection]], [[refraction]], etc.. However, they usually can model multiple ''layers'' (conceptually of ink, paper, or film; opaque, [[translucent]], or [[transparent]] -- stacked in a specific order. The ordering is usually defined by a single number (the layer's ''depth'', or distance from the viewer).

Layered models are sometimes called ''2 1/2-D computer graphics''. They make it possible to mimic traditional traftingdrafting and printing techniques based on film and paper, such as cutting and pasting; and allow the user to edit any layer without affecting the others. For these reasons, they are used in most [[graphical editors]]. Layered models also allow better [[anti-aliasing]] of complex drawings and a sound model for some popular modeling concepts such as [[mitered joints]] and the [[even-odd rule]].

In a layer-based model, the target image is produced by "painting" or "pasting" each layer, in order of decreasing depth, on a virtual ''canvas'' -- a [[digital image]] initially colored with an uniform [[background color]]. Painting one color over another at a particular [[pixel]] results in the second color, or in a combination of the two colors if the layer includes some transparency.