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In computer graphics, accounting for level of detail〔http://people.cs.clemson.edu/~dhouse/courses/405/notes/OpenGL-mipmaps.pdf〕〔http://computer-graphics.se/TSBK07-files/pdf/PDF09/10%20LOD.pdf〕〔http://rastergrid.com/blog/2010/10/gpu-based-dynamic-geometry-lod/〕 involves decreasing the complexity of a 3D object representation as it moves away from the viewer or according to other metrics such as object importance, viewpoint-relative speed or position. Level of detail techniques increase the efficiency of rendering by decreasing the workload on graphics pipeline stages, usually vertex transformations. The reduced visual quality of the model is often unnoticed because of the small effect on object appearance when distant or moving fast. Although most of the time LOD is applied to geometry detail only, the basic concept can be generalized. Recently, LOD techniques also included shader management to keep control of pixel complexity. A form of level of detail management has been applied to textures for years, under the name of mipmapping, also providing higher rendering quality. It is commonplace to say that "an object has been ''LOD'd''" when the object is simplified by the underlying ''LOD-ing algorithm''. ==Historical reference== The origin of all the LOD algorithms for 3D computer graphics can be traced back to an article by James H. Clark in the October 1976 issue of ''Communications of the ACM''. At the time, computers were monolithic and rare, and graphics was being driven by researchers. The hardware itself was completely different, both architecturally and performance-wise. As such, many differences could be observed with regard to today's algorithms but also many common points. The original algorithm presented a much more generic approach to what will be discussed here. After introducing some available algorithms for geometry management, it is stated that most fruitful gains came from ''"...structuring the environments being rendered"'', allowing to exploit faster transformations and clipping operations. The same environment structuring is now proposed as a way to control varying detail thus avoiding unnecessary computations, yet delivering adequate visual quality: The proposed algorithm envisions a tree data structure which encodes in its arcs both transformations and transitions to more detailed objects. In this way, each node encodes an object and according to a fast heuristic, the tree is descended to the leaves which provide each object with more detail. When a leaf is reached, other methods could be used when higher detail is needed, such as Catmull's recursive subdivision. The paper then introduces clipping (not to be confused with culling (computer although often similar), various considerations on the ''graphical working set'' and its impact on performance, interactions between the proposed algorithm and others to improve rendering speed. Interested readers are encouraged in checking the references for further details on the topic. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Level of detail」の詳細全文を読む スポンサード リンク
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