Name
gluNurbsCallback — define a callback for a NURBS object
C Specification
void gluNurbsCallback
| ( | GLUnurbs* nurb
, GLenum which
, _GLfuncptr CallBackFunc
); |
Python Specification
gluNurbsCallback
| ( |
nurb
,
which
,
CallBackFunc
) →
None
|
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
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 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 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
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 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
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 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
-
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, 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
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 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 available only if the GLU version is 1.3 or
greater.
Python Sample Code
- gluNurbsCallback
- GLU_NURBS_BEGIN
- GLU_NURBS_COLOR
- GLU_NURBS_END
- GLU_NURBS_TEXTURE_COORD
- GLU_NURBS_VERTEX