GLenum which,
_GLUfuncptr CallBackFunc )
PARAMETERS
nurb Specifies the NURBS object (created with
gluNewNurbsRenderer).
which Specifies 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.
CallBackFunc Specifies the function that the callback calls.
DESCRIPTION
gluNurbsCallback is used to define a callback to be used by a NURBS ob‐
ject. If the specified callback is already defined, then it is re‐
placed. If CallBackFunc is NULL, then this callback will not get in‐
voked 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 speci‐
fied 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_BEGIN
The 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:
void begin ( GLenum type );
GLU_NURBS_BEGIN_DATA
The same as the GLU_NURBS_BEGIN 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
gluNurbsCallbackData. The default callback function is NULL.
it takes an additional pointer argument. This pointer is a
copy of the pointer that was specified at the last call to
gluNurbsCallbackData. The default callback function is NULL.
The function prototype for this callback function looks like:
void vertexData ( GLfloat *vertex, void *userData );
GLU_NURBS_NORMAL
The normal callback is invoked as the vertex normal is gener‐
ated. The components of the normal are stored in the parame‐
ter ``normal''. In the case of a NURBS curve, the callback
function is effective only when the user provides a normal map
(GL_MAP1_NORMAL). In the case of a NURBS surface, if a normal
map (GL_MAP2_NORMAL) 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 GL_AUTO_NORMAL is enabled.
The default normal callback function is NULL. The function
prototype for this callback function looks like:
void normal ( GLfloat *normal );
GLU_NURBS_NORMAL_DATA
The same as the GLU_NURBS_NORMAL 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
gluNurbsCallbackData. The default callback function is NULL.
The function prototype for this callback function looks like:
void normalData ( GLfloat *normal, void *userData );
GLU_NURBS_COLOR
The color callback is invoked as the color of a vertex is gen‐
erated. The components of the color are stored in the parame‐
ter ``color''. This callback is effective only when the user
provides a color map (GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4).
``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 );
GLU_NURBS_COLOR_DATA
The same as the GLU_NURBS_COLOR 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
gluNurbsCallbackData. The default callback function is NULL.
The function prototype for this callback function looks like:
void colorData ( GLfloat *color, void *userData );
GLU_NURBS_TEXTURE_COORD
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 (GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2,
tion is NULL. The function prototype for this callback func‐
tion looks like:
void texCoordData (GLfloat *texCoord, void *userData);
GLU_NURBS_END
The end callback is invoked at the end of a primitive. The de‐
fault end callback function is NULL. The function prototype
for this callback function looks like:
void end ( void );
GLU_NURBS_END_DATA
This is the same as the GLU_NURBS_END 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
gluNurbsCallbackData. The default callback function is NULL.
The function prototype for this callback function looks like:
void endData ( void *userData );
GLU_NURBS_ERROR
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 GLU_NURBS_ERROR1 through GLU_NURBS_ERROR37. Char‐
acter strings describing these errors can be retrieved with
gluErrorString.
NOTES
gluNurbsCallback is available only if the GLU version is 1.2 or greater.
GLU version 1.2 supports only the GLU_ERROR parameter for which. The
GLU_ERROR value is deprecated in GLU version 1.3 in favor of
GLU_NURBS_ERROR. All other accepted values for CallBackFunc are avail‐
able only if the GLU version is 1.3 or greater.
SEE ALSO
gluErrorString, gluNewNurbsRenderer, gluNurbsCallbackData,
gluNurbsProperty
GLUNURBSCALLBACK(3G)
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