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Manual Reference Pages  - GLUNEXTCONTOUR (3G)

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gluNextContour - mark the beginning of another contour

CONTENTS

C Specification
Parameters
Description
Example
See Also

void gluNextContour( GLUtesselator* tess,

                   GLenum type )

tess	Specifies the tessellation object (created with  gluNewTess).
type	Specifies the type of the contour being defined. Valid values are  GLU_EXTERIOR,  GLU_INTERIOR,  GLU_UNKNOWN,  GLU_CCW, and  GLU_CW.

 gluNextContour is used in describing polygons with multiple contours. After the first contour has been described through a series of  gluTessVertex calls, a  gluNextContour call indicates that the previous contour is complete and that the next contour is about to begin. Another series of  gluTessVertex calls is then used to describe the new contour. This process can be repeated until all contours have been described.

type defines what type of contour follows. The legal contour types are as follows:

GLU_EXTERIOR	An exterior contour defines an exterior boundary of the polygon.
GLU_INTERIOR	An interior contour defines an interior boundary of the polygon (such as a hole).
GLU_UNKNOWN	An unknown contour is analyzed by the library to determine if it is interior or exterior.
GLU_CCW,  GLU_CW	The first  GLU_CCW or  GLU_CW contour defined is considered to be exterior. All other contours are considered to be exterior if they are oriented in the same direction (clockwise or counterclockwise) as the first contour, and interior if they are not.

If one contour is of type  GLU_CCW or  GLU_CW, then all contours must be of the same type (if they are not, then all  GLU_CCW and  GLU_CW contours will be changed to  GLU_UNKNOWN).

Note that there is no real difference between the  GLU_CCW and  GLU_CW contour types.

Before the first contour is described,  gluNextContour can be called to define the type of the first contour. If  gluNextContour is not called before the first contour, then the first contour is marked  GLU_EXTERIOR.

This command is obsolete and is provided for backward compatibility only. Calls to  gluNextContour are mapped to  gluTessEndContour followed by  gluTessBeginContour.

A quadrilateral with a triangular hole in it can be described as follows:

.Ex 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);
.Ee

 gluBeginPolygon(3G),  gluNewTess(3G),  gluTessCallback(3G),  gluTessVertex(3G),  gluTessBeginContour(3G)

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