gluTessVertex - specify a vertex on a polygon



C SPECIFICATION

       void gluTessVertex( GLUtesselator* tess,
                           GLdouble *location,
                           GLvoid* data )



PARAMETERS

       tess      Specifies  the tessellation object (created with
                 gluNewTess).

       location  Specifies the location of the vertex.

       data      Specifies an opaque pointer passed back  to  the
                 program  with  the vertex callback (as specified
                 by gluTessCallback).


DESCRIPTION

       gluTessVertex describes a vertex on  a  polygon  that  the
       program defines. Successive gluTessVertex calls describe a
       closed contour. For example, to describe  a  quadrilateral
       gluTessVertex  should be called four times.  gluTessVertex
       can  only  be  called  between   gluTessBeginContour   and
       gluTessEndContour.

       data  normally points to a structure containing the vertex
       location, as well as other per-vertex attributes  such  as
       color and normal.  This pointer is passed back to the user
       through the GLU_TESS_VERTEX or GLU_TESS_VERTEX_DATA  call-
       back after tessellation (see the gluTessCallback reference
       page).


EXAMPLE

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

       gluTessBeginPolygon(tobj, NULL);
        gluTessBeginContour(tobj);
          gluTessVertex(tobj, v1, v1);
          gluTessVertex(tobj, v2, v2);
          gluTessVertex(tobj, v3, v3);
          gluTessVertex(tobj, v4, v4);
        gluTessEndContour(tobj);
        gluTessBeginContour(tobj);
          gluTessVertex(tobj, v5, v5);
          gluTessVertex(tobj, v6, v6);
          gluTessVertex(tobj, v7, v7);
        gluTessEndContour(tobj); gluTessEndPolygon(tobj);


       but the very last set could be overwritten before  tessel-
       lation begins.

       Two common symptoms of this problem are consists of a sin-
       gle point (when a local variable is used for data)  and  a
       GLU_TESS_NEED_COMBINE_CALLBACK  error  (when a local vari-
       able is used for location).


SEE ALSO

       gluTessBeginPolygon,   gluNewTess,    gluTessBeginContour,
       gluTessCallback,      gluTessProperty,      gluTessNormal,
       gluTessEndPolygon





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