HP Workstation zx2000 OpenGL 1.1 Reference for HP-UX 11.x - Page 412

T gluTessCallback gluTessCallback gluTessCallback: define a callback for a tessellation object. C Specification void gluTessCallback( GLUtesselator* tess, GLenum which, GLvoid (*CallBackFunc)() Parameters tess which CallBackFunc Specifies the tessellation object (created with gluNewTess). Specifies the callback being defined. The following values are valid: GLU_TESS_BEGIN, GLU_TESS_BEGIN_DATA, GLU_TESS_EDGE_FLAG, GLU_TESS_EDGE_FLAG_DATA, GLU_TESS_VERTEX, GLU_TESS_VERTEX_DATA, GLU_TESS_END, GLU_TESS_END_DATA, GLU_TESS_COMBINE, GLU_TESS_COMBINE_DATA, GLU_TESS_ERROR, and GLU_TESS_ERROR_DATA. Specifies the function to be called. Description gluTessCallback is used to indicate a callback to be used by a tessellation object. If the specified callback is already defined, then it is replaced. If CallBackFunc is NULL, then the existing callback becomes undefined. These callbacks are used by the tessellation object to describe how a polygon specified by the user is broken into triangles. Note that there are two versions of each callback: one with user-specified polygon data and one without. If both versions of a particular callback are specified, then the callback with user-specified polygon data will be used. Note that the polygon_data parameter used by some of the functions is a copy of the pointer that was specified when gluTessBeginPolygon was called. The legal callbacks are as follows: GLU_TESS_BEGIN The begin callback is invoked like glBegin to indicate the start of a (triangle) primitive. The function takes a single argument of type GLenum. If the GLU_TESS_BOUNDARY_ONLY property is set to GL_FALSE, then the argument is set to either GL_TRIANGLE_FAN, GL_TRIANGLE_STRIP, or GL_TRIANGLES. If the GLU_TESS_BOUNDARY_ONLY property is set to GL_TRUE, then the argument will be set to GL_LINE_LOOP. The function prototype for this callback is: void begin(GLenum type); GLU_TESS_BEGIN_DATA 412 Chapter 18