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gluTessCallback
Chapter 18
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The same as the GLU_TESS_BEGIN callback except that it takes an additional pointer
argument. This pointer is identical to the opaque pointer provided when
gluTessBeginPolygon was called. The function prototype for this callback is:
void beginData(GLenum type, void *polygon_data);
GLU_TESS_EDGE_FLAG
The edge flag callback is similar to glEdgeFlag. The function takes a single boolean flag
that indicates which edges lie on the polygon boundary. If the flag is GL_TRUE, then
each vertex that follows begins an edge that lies on the polygon boundary, that is, an
edge that separates an interior region from an exterior one. If the flag is GL_FALSE,
then each vertex that follows begins an edge that lies in the polygon interior. The edge
flag callback (if defined) is invoked before the first vertex callback.
Since triangle fans and triangle strips do not support edge flags, the begin callback is
not called with GL_TRIANGLE_FAN or GL_TRIANGLE_STRIP if a non-NULL edge
flag callback is provided. (If the callback is initialized to NULL, there is no impact on
performance). Instead, the fans and strips are converted to independent triangles. The
function prototype for this callback is:
void edgeFlag(GLboolean flag);
GLU_TESS_EDGE_FLAG_DATA
The same as the GLU_TESS_EDGE_FLAG callback except that it takes an additional
pointer argument. This pointer is identical to the opaque pointer provided when
gluTessBeginPolygon was called. The function prototype for this callback is:
void edgeFlagData(GLboolean flag, void *polygon_data);
GLU_TESS_VERTEX
The vertex callback is invoked between the begin and end callbacks. It is similar to
glVertex, and it defines the vertices of the triangles created by the tessellation process.
The function takes a pointer as its only argument. This pointer is identical to the opaque
pointer provided by the user when the vertex was described (see gluTessVertex). The
function prototype for this callback is:
void vertex (void *vertex_data);
GLU_TESS_VERTEX_DATA
The same as the GLU_TESS_VERTEX callback except that it takes an additional
pointer argument. This pointer is identical to the opaque pointer provided when
gluTessBeginPolygon was called. The function prototype for this callback is:
void vertexData (void *vertex_data, void *polygon_data);
GLU_TESS_END
The end callback serves the same purpose as glEnd. It indicates the end of a primitive
and it takes no arguments. The function prototype for this callback is:
void end(void);
GLU_TESS_END_DATA
The same as the GLU_TESS_END callback except that it takes an additional pointer
argument. This pointer is identical to the opaque pointer provided when
gluTessBeginPolygon was called. The function prototype for this callback is:
void endData(void *polygon_data);