NAME

gluNurbsCallback - define a callback for a NURBS object

C SPECIFICATION

void gglluuNNuurrbbssCCaallllbbaacckk( GLUnurbs* _n_u_r_b,
                       GLenum _w_h_i_c_h,
                       _GLUfuncptr _C_a_l_l_B_a_c_k_F_u_n_c )

delim $$

PARAMETERS

_n_u_r_b
Specifies the NURBS object (created with gglluuNNeewwNNuurrbbssRReennddeerreerr).
_w_h_i_c_h
Specifies the callback being defined. Valid values are GGLLUU__NNUURRBBSS__BBEEGGIINN, GGLLUU__NNUURRBBSS__VVEERRTTEEXX, GGLLUU__NNUURRBBSS__NNOORRMMAALL, GGLLUU__NNUURRBBSS__CCOOLLOORR, GGLLUU__NNUURRBBSS__TTEEXXTTUURREE__CCOOOORRDD, GGLLUU__NNUURRBBSS__EENNDD, GGLLUU__NNUURRBBSS__BBEEGGIINN__DDAATTAA, GGLLUU__NNUURRBBSS__VVEERRTTEEXX__DDAATTAA, GGLLUU__NNUURRBBSS__NNOORRMMAALL__DDAATTAA, GGLLUU__NNUURRBBSS__CCOOLLOORR__DDAATTAA, GGLLUU__NNUURRBBSS__TTEEXXTTUURREE__CCOOOORRDD__DDAATTAA, GGLLUU__NNUURRBBSS__EENNDD__DDAATTAA, and GGLLUU__NNUURRBBSS__EERRRROORR.
_C_a_l_l_B_a_c_k_F_u_n_c
Specifies the function that the callback calls.

DESCRIPTION

gglluuNNuurrbbssCCaallllbbaacckk 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 _C_a_l_l_B_a_c_k_F_u_n_c 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 GGLLUU__NNUURRBBSS__MMOODDEE is set to be GGLLUU__NNUURRBBSS__TTEESSSSEELLLLAATTOORR) 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 gglluuNNuurrbbssCCaallllbbaacckkDDaattaa.

The error callback function is effective no matter which value that GGLLUU__NNUURRBBSS__MMOODDEE is set to. All other callback functions are effective only when GGLLUU__NNUURRBBSS__MMOODDEE is set to GGLLUU__NNUURRBBSS__TTEESSSSEELLLLAATTOORR.

The legal callbacks are as follows:

GGLLUU__NNUURRBBSS__BBEEGGIINN
The begin callback indicates the start of a primitive. The function takes a single argument of type GLenum, which can be one of GGLL__LLIINNEESS, GGLL__LLIINNEE__SSTTRRIIPP, GGLL__TTRRIIAANNGGLLEE__FFAANN, GGLL__TTRRIIAANNGGLLEE__SSTTRRIIPP, GGLL__TTRRIIAANNGGLLEESS, or GGLL__QQUUAADD__SSTTRRIIPP. The default begin callback function is NULL. The function prototype for this callback looks like: void begin ( GLenum type );
GGLLUU__NNUURRBBSS__BBEEGGIINN__DDAATTAA
The same as the GGLLUU__NNUURRBBSS__BBEEGGIINN callback except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void beginData (GLenum type, void *userData);
GGLLUU__NNUURRBBSS__VVEERRTTEEXX
The vertex callback indicates a vertex of the primitive. The coordinates of the vertex are stored in the parameter ``vertex''. All the generated vertices have dimension 3, that is, homogeneous coordinates have been transformed into affine coordinates. The default vertex callback function is NULL. The function prototype for this callback function looks like: void vertex ( GLfloat *vertex );
GGLLUU__NNUURRBBSS__VVEERRTTEEXX__DDAATTAA
This is the same as the GGLLUU__NNUURRBBSS__VVEERRTTEEXX callback, except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void vertexData ( GLfloat *vertex, void *userData );
GGLLUU__NNUURRBBSS__NNOORRMMAALL
The normal callback is invoked as the vertex normal is generated. The components of the normal are stored in the parameter ``normal''. In the case of a NURBS curve, the callback function is effective only when the user provides a normal map (GGLL__MMAAPP11__NNOORRMMAALL). In the case of a NURBS surface, if a normal map (GGLL__MMAAPP22__NNOORRMMAALL) is provided, then the generated normal is computed from the normal map. If a normal map is not provided then a surface normal is computed in a manner similar to that described for evaluators when GGLL__AAUUTTOO__NNOORRMMAALL is enabled. The default normal callback function is NULL. The function prototype for this callback function looks like: void normal ( GLfloat *normal );
GGLLUU__NNUURRBBSS__NNOORRMMAALL__DDAATTAA
The same as the GGLLUU__NNUURRBBSS__NNOORRMMAALL callback except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void normalData ( GLfloat *normal, void *userData );
GGLLUU__NNUURRBBSS__CCOOLLOORR
The color callback is invoked as the color of a vertex is generated. The components of the color are stored in the parameter ``color''. This callback is effective only when the user provides a color map (GGLL__MMAAPP11__CCOOLLOORR__44 or GGLL__MMAAPP22__CCOOLLOORR__44). ``color'' contains four components: R,G,B,A. The default color callback function is NULL. The prototype for this callback function looks like: void color ( GLfloat *color );
GGLLUU__NNUURRBBSS__CCOOLLOORR__DDAATTAA
The same as the GGLLUU__NNUURRBBSS__CCOOLLOORR callback except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void colorData ( GLfloat *color, void *userData );
GGLLUU__NNUURRBBSS__TTEEXXTTUURREE__CCOOOORRDD
The texture callback is invoked as the texture coordinates of a vertex are generated. These coordinates are stored in the parameter ``texCoord''. The number of texture coordinates can be 1, 2, 3, or 4 depending on which type of texture map is specified (GGLL__MMAAPP11__TTEEXXTTUURREE__CCOOOORRDD__11, GGLL__MMAAPP11__TTEEXXTTUURREE__CCOOOORRDD__22, GGLL__MMAAPP11__TTEEXXTTUURREE__CCOOOORRDD__33, GGLL__MMAAPP11__TTEEXXTTUURREE__CCOOOORRDD__44, GGLL__MMAAPP22__TTEEXXTTUURREE__CCOOOORRDD__11, GGLL__MMAAPP22__TTEEXXTTUURREE__CCOOOORRDD__22, GGLL__MMAAPP22__TTEEXXTTUURREE__CCOOOORRDD__33, GGLL__MMAAPP22__TTEEXXTTUURREE__CCOOOORRDD__44). If no texture map is specified, this callback function will not be called. The default texture callback function is NULL. The function prototype for this callback function looks like: void texCoord ( GLfloat *texCoord );
GGLLUU__NNUURRBBSS__TTEEXXTTUURREE__CCOOOORRDD__DDAATTAA
This is the same as the GGLLUU__NNUURRBBSS__TTEEXXTTUURREE__CCOOOORRDD callback, except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void texCoordData (GLfloat *texCoord, void *userData);
GGLLUU__NNUURRBBSS__EENNDD
The end callback is invoked at the end of a primitive. The default end callback function is NULL. The function prototype for this callback function looks like: void end ( void );
GGLLUU__NNUURRBBSS__EENNDD__DDAATTAA
This is the same as the GGLLUU__NNUURRBBSS__EENNDD callback, except that it takes an additional pointer argument. This pointer is a copy of the pointer that was specified at the last call to gglluuNNuurrbbssCCaallllbbaacckkDDaattaa. The default callback function is NULL. The function prototype for this callback function looks like: void endData ( void *userData );
GGLLUU__NNUURRBBSS__EERRRROORR
The error function is called when an error is encountered. Its single argument is of type GLenum, and it indicates the specific error that occurred. There are 37 errors unique to NURBS named GGLLUU__NNUURRBBSS__EERRRROORR11 through GGLLUU__NNUURRBBSS__EERRRROORR3377. Character strings describing these errors can be retrieved with gglluuEErrrroorrSSttrriinngg.

NOTES

gglluuNNuurrbbssCCaallllbbaacckk is available only if the GLU version is 1.2 or greater.

GLU version 1.2 supports only the GGLLUU__EERRRROORR parameter for _w_h_i_c_h. The GGLLUU__EERRRROORR value is deprecated in GLU version 1.3 in favor of GGLLUU__NNUURRBBSS__EERRRROORR. All other accepted values for _C_a_l_l_B_a_c_k_F_u_n_c are available only if the GLU version is 1.3 or greater.

SEE ALSO

gglluuEErrrroorrSSttrriinngg((33GG)), gglluuNNeewwNNuurrbbssRReennddeerreerr((33GG)), gglluuNNuurrbbssCCaallllbbaacckkDDaattaa((33GG)), gglluuNNuurrbbssPPrrooppeerrttyy((33GG))