GLUNURBSCALLBACK - Online Linux Manual PageSection : 3G NAME"gluNurbsCallback − define a callback for a NURBS object C SPECIFICATIONvoid gluNurbsCallback( GLUnurbs* nurb, GLenum which,
_GLUfuncptr CallBackFunc)PARAMETERSnurbSpecifies the NURBS object (created with gluNewNurbsRenderer). whichSpecifies the callback being defined. Valid values are GLU_NURBS_BEGIN, GLU_NURBS_VERTEX, GLU_NURBS_NORMAL, GLU_NURBS_COLOR, GLU_NURBS_TEXTURE_COORD, GLU_NURBS_END, GLU_NURBS_BEGIN_DATA, GLU_NURBS_VERTEX_DATA, GLU_NURBS_NORMAL_DATA, GLU_NURBS_COLOR_DATA, GLU_NURBS_TEXTURE_COORD_DATA, GLU_NURBS_END_DATA, and GLU_NURBS_ERROR. CallBackFuncSpecifies the function that the callback calls. DESCRIPTIONgluNurbsCallback is used to define a callback to be used by a NURBS object. If the specified callback is already defined, then it is replaced. If CallBackFunc is NULL, then this callback will not get invoked and the related data, if any, will be lost. Except the error callback, these callbacks are used by NURBS tessellator (when GLU_NURBS_MODE is set to be GLU_NURBS_TESSELLATOR) to return back the OpenGL polygon primitives resulting from the tessellation. Note that there are two versions of each callback: one with a user data pointer and one without. If both versions for a particular callback are specified then the callback with the user data pointer will be used. Note that ``userData'' is a copy of the pointer that was specified at the last call to gluNurbsCallbackData. The error callback function is effective no matter which value that GLU_NURBS_MODE is set to. All other callback functions are effective only when GLU_NURBS_MODE is set to GLU_NURBS_TESSELLATOR. The legal callbacks are as follows: GLU_NURBS_BEGINThe begin callback indicates the start of a primitive. The function takes a single argument of type GLenum, which can be one of GL_LINES, GL_LINE_STRIP, GL_TRIANGLE_FAN, GL_TRIANGLE_STRIP, GL_TRIANGLES, or GL_QUAD_STRIP. The default begin callback function is NULL. The function prototype for this callback looks like: