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The Weiler–Atherton is a polygon clipping algorithm. It is used in the areas like computer graphics, games development and others where clipping of polygon is needed. It allows clipping of a ''subject or candidate polygon'' by an arbitrarily shaped ''clipping polygon/area/region''. It is generally applicable only in 2D. However, it can be used in 3D through visible surface determination and with improved efficiency through Z-ordering.〔Foley, James, Andries van Dam, Steven Feiner, and John Hughes. "Computer Graphics: Principle and Practice". Addison-Wesley Publishing Company. Reading, Massachusetts: 1987. pages 689-693〕 == Prelude == Before applying to any polygon, the algorithm requires several preconditions to be fulfilled. - Candidate polygons need to be oriented clockwise. - Candidate polygons should not be self intersecting (i.e. re-entrant). - The algorithm can support holes (as counter-clockwise polygons wholly inside their parent polygon), but requires additional algorithms to decide which polygons are holes. Then, merging of polygons can be performed by a variant of the algorithm. 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「Weiler–Atherton clipping algorithm」の詳細全文を読む スポンサード リンク
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