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Cube mapping
In computer graphics, cube mapping is a method of environment mapping that uses the six faces of a cube as the map shape. The environment is projected onto the sides of a cube and stored as six square textures, or unfolded into six regions of a single texture. The cube map is generated by first rendering the scene six times from a viewpoint, with the views defined by an 90 degree view frustum representing each cube face.〔Fernando, R. & Kilgard M. J. (2003). The CG Tutorial: The Definitive Guide to Programmable Real-Time Graphics. (1st ed.). Addison-Wesley Longman Publishing Co., Inc. Boston, MA, USA. Chapter 7: Environment Mapping Techniques〕
In the majority of cases, cube mapping is preferred over the older method of sphere mapping because it eliminates many of the problems that are inherent in sphere mapping such as image distortion, viewpoint dependency, and computational inefficiency. Also, cube mapping provides a much larger capacity to support real-time rendering of reflections relative to sphere mapping because the combination of inefficiency and viewpoint dependency severely limit the ability of sphere mapping to be applied when there is a consistently changing viewpoint.
==History==
Cube mapping was first proposed in 1986 by Ned Greene in his paper “Environment Mapping and Other Applications of World Projections”,〔Greene, N. 1986. Environment mapping and other applications of world projections. IEEE Comput. Graph. Appl. 6, 11 (Nov. 1986), 21-29. (http://dx.doi.org/10.1109/MCG.1986.276658 )〕 ten years after environment mapping was first put forward by Jim Blinn and Martin Newell. However, hardware limitations on the ability to access six texture images simultaneously made it infeasible to implement cube mapping without further technological developments. This problem was remedied in 1999 with the release of the Nvidia GeForce 256. Nvidia touted cube mapping in hardware as “a breakthrough image quality feature of GeForce 256 that ... will allow developers to create accurate, real-time reflections. Accelerated in hardware, cube environment mapping will free up the creativity of developers to use reflections and specular lighting effects to create interesting, immersive environments.”〔Nvidia, Jan 2000. Technical Brief: (Perfect Reflections and Specular Lighting Effects With Cube Environment Mapping )〕 Today, cube mapping is still used in a variety of graphical applications as a favored method of environment mapping.
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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