gluNurbsCallback() gluNurbsCallback()
gluNurbsCallback - define a callback for a NURBS object
void gluNurbsCallback(
GLUnurbs* nurb,
GLenum which,
GLvoid (*CallBackFunc) );
Specifies the NURBS object (created with gluNewNurbsRenderer()).
Specifies 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 callback calls.
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 GLU_NURBS_MODE_EXT is set to be
GLU_NURBS_TESSELLATOR_EXT) 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 GLU_NURBS_MODE_EXT is set to. All other callback
functions are effective 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 gluNurbsCallbackDataEXT(). The
default callback function is NULL. The function 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, 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 ); The same as the GLU_NURBS_VERTEX_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 function is NULL. The
function prototype for this callback function looks like:
void vertexData(
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
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 ); 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
(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 ); 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 gluNurbsCallbackDataEXT().
The default callback function is
NULL. The function prototype for this callback function
looks like: void colorData(
GLfloat *color,
void *userData ); 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_MAP*_TEXTURE_COORD_1, GL_MAP*_TEXTURE_COORD_2,
GL_MAP*_TEXTURE_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_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
gluNurbsCallbackDataEXT(). The default callback function
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 prototype 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 gluNurbsCallbackDataEXT().
The default callback function is NULL. The
function 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().
gluErrorString(3), gluNewNurbsRenderer(3)
gluNurbsCallback()
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