gluBeginPolygon

王朝百科·作者佚名 2010-03-06

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NAME

gluBeginPolygon, gluEndPolygon - delimit a polygon description

C SPECIFICATION

void gluBeginPolygon( GLUtriangulatorObj *tobj )

void gluEndPolygon( GLUtriangulatorObj *tobj )

PARAMETERS

tobj ? Specifies the tessellation object (created with gluNewTess).

DESCRIPTION

gluBeginPolygon and gluEndPolygon delimit the definition of a nonconvex polygon. To define such a polygon, first call gluBeginPolygon. Then define the contours of the polygon by calling gluTessVertex for each vertex and gluNextContour to start each new contour. Finally, call gluEndPolygon to signal the end of the definition. See the "gluTessVertex" and "gluNextContour" reference pages for more details.

Once gluEndPolygon is called, the polygon is tessellated, and the resulting triangles are described through callbacks. See "gluTessCallback" for descriptions of the callback functions.

EXAMPLE

A quadrilateral with a triangular hole in it can be described like this:

gluBeginPolygon(tobj);

gluTessVertex(tobj, v1, v1);

gluTessVertex(tobj, v2, v2);

gluTessVertex(tobj, v3, v3);

gluTessVertex(tobj, v4, v4);

gluNextContour(tobj, GLU_INTERIOR);

gluTessVertex(tobj, v5, v5);

gluTessVertex(tobj, v6, v6);

gluTessVertex(tobj, v7, v7);

gluEndPolygon(tobj);