GLUNURBSCALLBACK(3G) 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 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 object. If the specified call-back callback
back 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 is set
to be GLU_NURBS_TESSELLATOR) to return back the OpenGL polygon primitives resulting from the tessel-lation. tessellation.
lation. Note that there are two versions of each callback: one with a user data pointer and one with-out. without.
out. 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 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 argu-ment. argument.
ment. 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 beginData (GLenum type, void *userData);
GLU_NURBS_VERTEX
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
This is the same as the GLU_NURBS_VERTEX 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 vertexData ( GLfloat *vertex, void *userData );
GLU_NURBS_NORMAL
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_NURBS_NORMAL_DATA
The same as the GLU_NURBS_NORMAL callback except that it takes an additional pointer argu-ment. argument.
ment. 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 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 compo-nents: components:
nents: R,G,B,A. The default color callback function is NULL. The prototype for this call-back callback
back 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 argu-ment. argument.
ment. 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_1,
GL_MAP1_TEXTURE_COORD_1, GL_MAP1_TEXTURE_COORD_2, GL_MAP1_TEXTURE_COORD_3,
GL_MAP1_TEXTURE_COORD_4, GL_MAP2_TEXTURE_COORD_1, GL_MAP2_TEXTURE_COORD_2,
GL_MAP2_TEXTURE_COORD_3, GL_MAP2_TEXTURE_COORD_4). 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
This is the same as the GLU_NURBS_TEXTURE_COORD callback, except that it takes an addi-tional additional
tional 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 texCoordData (GLfloat *texCoord, void *userData);
GLU_NURBS_END
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_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. Character 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 available
able only if the GLU version is 1.3 or greater.
SEE ALSO
gluErrorString(3G), gluNewNurbsRenderer(3G), gluNurbsCallbackData(3G), gluNurbsProperty(3G)
GLUNURBSCALLBACK(3G)
|