Signature
Parameters
| Variables | Description |
|---|---|
| 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).
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);
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
dereferenced until
gluTessEndPolygon
is executed,
all the vertex coordinates but the very last set could be overwritten
before tessellation begins.
See Also
Copyright
Copyright
1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
http://oss.sgi.com/projects/FreeB/
.
Sample Code References
The following code samples have been found which appear to reference the functions described here. Take care that the code may be old, broken or not even use PyOpenGL.
gluTessVertex