gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
NAME
gluNurbsCallback - define a callback for a NURBS object
C SPECIFICATION
void gluNurbsCallback( GLUnurbs* nurb,
GLenum which,
GLvoid (*CallBackFunc)( )
PARAMETERS
nurb Specifies the NURBS object (created with
gluNewNurbsRenderer).
which Specifies the callback being defined. Valid values are
GLUNURBSBEGINEXT, GLUNURBSVERTEXEXT, GLUNORMALEXT,
GLUNURBSCOLOREXT, GLUNURBSTEXTURECOORDEXT,
GLUENDEXT, GLUNURBSBEGINDATAEXT,
GLUNURBSVERTEXDATAEXT, GLUNORMALDATAEXT,
GLUNURBSCOLORDATAEXT, GLUNURBSTEXTURECOORDDATAEXT,
GLUENDDATAEXT, and GLUERROR.
CallBackFunc Specifies the function that the callback calls.
DESCRIPTION
gluNurbsCallback 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 GLUNURBSMODEEXT is set to be GLUNURBSTESSELLATOREXT) to
return back the openGL polygon primitives resulted 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 gluNurbsCallbackDataEXT.
The error callback function is effective no matter which value that
GLUNURBSMODEEXT is set to. All other callback functions are effective
only when GLUNURBSMODEEXT is set to GLUNURBSTESSELLATOREXT.
The legal callbacks are as follows:
GLUNURBSBEGINEXT
The begin callback indicates the start of a primitive. The
function takes a single argument of type GLenum which can be
one of GLLINES, GLLINESTRIPS, GLTRIANGLEFAN,
GLTRIANGLESTRIP, GLTRIANGLES, or GLQUADSTRIP. The default
begin callback function is NULL. The function prototype for
this callback looks like:
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
void begin ( GLenum type );
GLUNURBSBEGINDATAEXT
The same as the GLUNURBSBEGINEXT 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
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void beginData (GLenum type, void *userData);
GLUNURBSVERTEXEXT
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 );
GLUNURBSVERTEXDATAEXT
The same as the GLUNURBSVERTEXEXT 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
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void vertexData ( GLfloat *vertex, void *userData );
GLUNORMALEXT
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
(GLMAP1NORMAL). In the case of a NURBS surface, if a normal
map (GLMAP2NORMAL) 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 GLAUTONORMAL is enabled. The
default normal callback function is NULL. The function
prototype for this callback function looks like:
void normal ( GLfloat *normal );
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
GLUNORMALDATAEXT
The same as the GLUNURBSNORMALEXT 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
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void normalData ( GLfloat *normal, void *userData );
GLUNURBSCOLOREXT
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 (GLMAP1COLOR4 or GLMAP2COLOR4).
"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 );
GLUNURBSCOLORDATAEXT
The same as the GLUNURBSCOLOREXT 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
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void colorData ( GLfloat *color, void *userData );
GLUNURBSTEXTURECOORDEXT
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 (GLMAP*TEXTURECOORD1, GLMAP*TEXTURECOORD2,
GLMAP*TEXTURECOORD3, GLMAP*TEXTURECOORD4 where * can be
either 1 or 2). 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 );
GLUNURBSTEXTURECOORDDATAEXT
The same as the GLUNURBSTEXTURECOORDEXT callback except
that it takes an additional pointer argument. This pointer is a
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
copy of the pointer that was specified at the last call to
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void texCoordData (GLfloat *texCoord, void *userData);
GLUENDEXT
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 );
GLUENDDATAEXT
The same as the GLUNURBSTEXTURECOORDEXT 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
gluNurbsCallbackDataEXT. The default callback function is
NULL. The function prototype for this callback function looks
like:
void endData ( void *userData );
GLUERROR 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 GLUNURBSERROR1 through GLUNURBSERROR37.
Character strings describing these errors can be retrieved with
gluErrorString.
SEE ALSO
gluErrorString, gluNewNurbsRenderer
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