gluNurbsCallback()gluNurbsCallback()NAMEgluNurbsCallback - define a callback for a NURBS object
SYNOPSIS
void gluNurbsCallback(
GLUnurbs* nurb,
GLenum which,
GLvoid (*CallBackFunc) );
PARAMETERS
Specifies the NURBS object (created with gluNewNurbsRenderer()). Spec‐
ifies the callback being defined. Valid values are GLU_NURBS_BEGIN_EXT,
GLU_NURBS_VERTEX_EXT, GLU_NORMAL_EXT, GLU_NURBS_COLOR_EXT,
GLU_NURBS_TEXTURE_COORD_EXT, GLU_END_EXT, GLU_NURBS_BEGIN_DATA_EXT,
GLU_NURBS_VERTEX_DATA_EXT, GLU_NORMAL_DATA_EXT,
GLU_NURBS_COLOR_DATA_EXT, GLU_NURBS_TEXTURE_COORD_DATA_EXT,
GLU_END_DATA_EXT, and GLU_ERROR. Specifies the function that the call‐
back 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 tessella‐
tor (when GLU_NURBS_MODE_EXT is set to be GLU_NURBS_TESSELLATOR_EXT) to
return back the openGL polygon primitives resulted from the tessella‐
tion. 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
GLU_NURBS_MODE_EXT is set to. All other callback functions are effec‐
tive only when GLU_NURBS_MODE_EXT is set to GLU_NURBS_TESSELLATOR_EXT.
The legal callbacks are as follows: 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_STRIPS, 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 ); The same as the GLU_NURBS_BEGIN_EXT 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 gluNurb‐
sCallbackDataEXT(). The default callback function is NULL. The func‐
tion prototype for this callback function looks like: void beginData(
GLenum type,
void *userData ); 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, homoge‐
neous 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 ); The same as the GLU_NURBS_VERTEX_EXT call‐
back 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 vertex‐
Data(
GLfloat *vertex,
void *userData ); 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 (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 ); The same as the GLU_NURBS_NORMAL_EXT call‐
back 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 normal‐
Data(
GLfloat *normal,
void *userData ); 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 pro‐
vides a color map (GL_MAP1_COLOR_4 or GL_MAP2_COLOR_4). "color" con‐
tains 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 ); The same as the GLU_NURBS_COLOR_EXT 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 gluNurb‐
sCallbackDataEXT(). The default callback function is NULL. The func‐
tion prototype for this callback function looks like: void colorData(
GLfloat *color,
void *userData ); The texture callback is invoked as the tex‐
ture 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 speci‐
fied (GL_MAP*_TEXTURE_COORD_1, GL_MAP*_TEXTURE_COORD_2, GL_MAP*_TEX‐
TURE_COORD_3, GL_MAP*_TEXTURE_COORD_4 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 ); The same as the GLU_NURBS_TEX‐
TURE_COORD_EXT 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 func‐
tion is NULL. The function prototype for this callback function looks
like: void texCoordData(
GLfloat *texCoord,
void *userData ); The end callback is invoked at the end of a
primitive. The default end callback function is NULL. The function pro‐
totype for this callback function looks like: void end(
void ); The same as the GLU_NURBS_TEXTURE_COORD_EXT 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 gluNurb‐
sCallbackDataEXT(). The default callback function is NULL. The func‐
tion prototype for this callback function looks like: void endData(
void *userData ); 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. Character strings
describing these errors can be retrieved with gluErrorString().
SEE ALSOgluErrorString(3), gluNewNurbsRenderer(3)gluNurbsCallback()
