gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
gluNurbsCallback - define a callback for a NURBS object
void gluNurbsCallback( GLUnurbs* nurb,
GLenum which,
GLvoid (*CallBackFunc)( )
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.
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 [Toc] [Back]
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:
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
void begin ( GLenum type );
GLU_NURBS_BEGIN_DATA [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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.
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
The default normal callback function is NULL. The function
prototype for this callback function looks like:
void normal ( GLfloat *normal );
GLU_NURBS_NORMAL_DATA [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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.
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
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 [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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 [Toc] [Back]
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.
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gluNurbsCallback(3G) OpenGL Reference gluNurbsCallback(3G)
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.
gluErrorString, gluNewNurbsRenderer, gluNurbsCallbackData,
gluNurbsProperty
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