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gluNurbsCallback()
NAME
gluNurbsCallback - define a callback for a NURBS object
SYNOPSIS
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
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.
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 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:
GLU_NURBS_BEGIN_EXT
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 );
GLU_NURBS_BEGIN_DATA_EXT
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 );
GLU_NURBS_VERTEX_EXT
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 );
GLU_NURBS_VERTEX_DATA_EXT
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 );
GLU_NORMAL_EXT
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 );
GLU_NORMAL_DATA_EXT
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 );
GLU_NURBS_COLOR_EXT
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 );
GLU_NURBS_COLOR_DATA_EXT
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 );
GLU_NURBS_TEXTURE_COORD_EXT
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 );
GLU_NURBS_TEXTURE_COORD_DATA_EXT
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 );
GLU_END_EXT
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 );
GLU_END_DATA_EXT
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 );
GLU_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. Character strings describing these errors
can be retrieved with gluErrorString().
SEE ALSO
gluErrorString(3), gluNewNurbsRenderer(3)
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