GLUNURBSCALLBACK(3G)UNIX Programmer's Manual GLUNURBSCALLBACK(3G)
gluNurbsCallback - define a callback for a NURBS object
void gluNurbsCallback( GLUnurbs* nurb,
GLenum which,
_GLUfuncptr 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
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GLUNURBSCALLBACK(3G)UNIX Programmer's Manual GLUNURBSCALLBACK(3G)
The begin callback indicates the start of a primi-
tive. 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 speci-
fied at the last call to gluNurbsCallbackData.
The default callback function is NULL. The func-
tion 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 gen-
erated vertices have dimension 3, that is, homo-
geneous 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 argu-
ment. This pointer is a copy of the pointer that
was specified at the last call to
gluNurbsCallbackData. The default callback func-
tion 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 nor-
mal 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 sur-
face normal is computed in a manner similar to
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GLUNURBSCALLBACK(3G)UNIX Programmer's Manual GLUNURBSCALLBACK(3G)
that described for evaluators when GL_AUTO_NORMAL
is enabled.
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GLUNURBSCALLBACK(3G)UNIX Programmer's Manual 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
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 speci-
fied at the last call to gluNurbsCallbackData.
The default callback function is NULL. The func-
tion 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 call-
back 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 pro-
totype 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 speci-
fied at the last call to gluNurbsCallbackData.
The default callback function is NULL. The func-
tion 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 coor-
dinates 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)UNIX Programmer's Manual 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
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 func-
tion is NULL. The function prototype for this
callback function looks like:
void texCoordData (GLfloat *texCoord, void *user-
Data);
GLU_NURBS_END
The end callback is invoked at the end of a primi-
tive. 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 argu-
ment. This pointer is a copy of the pointer that
was specified at the last call to
gluNurbsCallbackData. The default callback func-
tion 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 GLe-
num, 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)UNIX Programmer's Manual 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(3G), gluNewNurbsRenderer(3G),
gluNurbsCallbackData(3G), gluNurbsProperty(3G)
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