HP c3700 - Workstation, Reference Manual, Page: 420 / 486

T
gluTessVertex
Chapter 18
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gluTessVertex
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 callback after
tessellation (see the gluTessCallback reference page).
Notes
It is a common error to use a local variable for location or data and store values into it as
part of a loop. For example:
for (i = 0; i < NVERTICES; ++i) {
GLdouble data[3];
data[0] = vertex[i][0];
data[1] = vertex[i][1];
data[2] = vertex[i][2];
gluTessVertex(tobj, data, data);
}
This doesn’t work, because the pointers specified by location and data might not be
de-referenced until gluTessEndPolygon is executed, all the vertex coordinates but the
very last set could be overwritten before tessellation begins.