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In technical applications of 3D computer graphics (CAx) such as computer-aided design and computer-aided manufacturing, surfaces are one way of representing objects. The other ways are wireframe (lines and curves) and solids. Point clouds are also sometimes used as temporary ways to represent an object, with the goal of using the points to create one or more of the three permanent representations. ==Open and closed surfaces== If one considers a local parametrization of a surface: : then the curves obtained by varying ''u'' while keeping ''v'' fixed are sometimes called the ''u'' flow lines. The curves obtained by varying ''v'' while ''u'' is fixed are called the ''v'' flow lines. These are generalizations of the ''x'' and ''y'' lines in the plane and of the meridians and circles of latitude on a sphere. Open surfaces are not closed in either direction. This means moving in any direction along the surface will cause an observer to hit the edge of the surface. The top of a car hood is an example of a surface open in both directions. 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「Computer representation of surfaces」の詳細全文を読む スポンサード リンク
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