229 lines
8.5 KiB
Plaintext
229 lines
8.5 KiB
Plaintext
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'\" e
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'\"! eqn | mmdoc
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'\"macro stdmacro
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.ds Vn Version 1.2
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.ds Dt 6 March 1997
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.ds Re Release 1.2.0
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.ds Dp May 02 11:53
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.ds Dm 37 nurbscall
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.ds Xs 14092 10 nurbscallback.gl
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.TH GLUNURBSCALLBACK 3G
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.SH NAME
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.B "gluNurbsCallback
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\- define a callback for a NURBS object
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.SH C SPECIFICATION
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void \f3gluNurbsCallback\fP(
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GLUnurbs* \fInurb\fP,
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.nf
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.ta \w'\f3void \fPgluNurbsCallback( 'u
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GLenum \fIwhich\fP,
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_GLUfuncptr \fICallBackFunc\fP )
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.fi
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.EQ
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delim $$
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.EN
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.SH PARAMETERS
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.TP \w'\fICallBackFunc\fP\ \ 'u
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\f2nurb\fP
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Specifies the NURBS object (created with \%\f3gluNewNurbsRenderer\fP).
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.TP
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\f2which\fP
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Specifies the callback being defined.
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Valid values are \%\f3GLU_NURBS_BEGIN\fP, \%\f3GLU_NURBS_VERTEX\fP, \%\f3GLU_NURBS_NORMAL\fP, \%\f3GLU_NURBS_COLOR\fP, \%\f3GLU_NURBS_TEXTURE_COORD\fP, \%\f3GLU_NURBS_END\fP, \%\f3GLU_NURBS_BEGIN_DATA\fP, \%\f3GLU_NURBS_VERTEX_DATA\fP, \%\f3GLU_NURBS_NORMAL_DATA\fP, \%\f3GLU_NURBS_COLOR_DATA\fP, \%\f3GLU_NURBS_TEXTURE_COORD_DATA\fP, \%\f3GLU_NURBS_END_DATA\fP, and \%\f3GLU_NURBS_ERROR\fP.
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.TP
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\f2CallBackFunc\fP
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Specifies the function that the callback calls.
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.SH DESCRIPTION
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\%\f3gluNurbsCallback\fP is used to define a callback to be used by a NURBS
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object.
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If the specified callback is already defined, then it is replaced. If
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\f2CallBackFunc\fP is NULL, then this callback will not get
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invoked and the related data, if any, will be lost.
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.P
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Except the error callback, these callbacks are used by NURBS tessellator (when \%\f3GLU_NURBS_MODE\fP is set to be \%\f3GLU_NURBS_TESSELLATOR\fP) to return back the OpenGL
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polygon primitives resulting from the tessellation. Note that there are two
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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
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the user data pointer will be used. Note that ``userData'' is a copy of the pointer that was specified at the last call to \%\f3gluNurbsCallbackData\fP.
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.P
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The error callback function is effective no matter which value that
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\%\f3GLU_NURBS_MODE\fP is set to.
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All other callback functions are effective only when \%\f3GLU_NURBS_MODE\fP
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is set to \%\f3GLU_NURBS_TESSELLATOR\fP.
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.P
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The legal callbacks are as follows:
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.TP 10
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\%\f3GLU_NURBS_BEGIN\fP
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The begin callback indicates the start of a primitive. The function
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takes a single argument of type GLenum, which can be one of
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\%\f3GL_LINES\fP, \%\f3GL_LINE_STRIP\fP, \%\f3GL_TRIANGLE_FAN\fP, \%\f3GL_TRIANGLE_STRIP\fP, \%\f3GL_TRIANGLES\fP, or \%\f3GL_QUAD_STRIP\fP. The
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default begin callback function is NULL. The function prototype
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for this callback looks like:
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.RS
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.Ex
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void begin ( GLenum type );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_BEGIN_DATA\fP
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The same as the \%\f3GLU_NURBS_BEGIN\fP callback except that it takes an
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additional pointer argument. This pointer is a copy of the pointer that
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was specified at the last call to \%\f3gluNurbsCallbackData\fP. The
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default callback function is NULL. The function prototype for this
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callback function looks like:
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.RS
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.Ex
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void beginData (GLenum type, void *userData);
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_VERTEX\fP
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The vertex callback indicates a vertex of the primitive. The
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coordinates of the vertex are stored in the parameter ``vertex''. All
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the generated vertices have dimension 3, that is, homogeneous
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coordinates have been transformed into affine coordinates. The default
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vertex callback function is NULL. The function prototype for this
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callback function looks like:
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.RS
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.Ex
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void vertex ( GLfloat *vertex );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_VERTEX_DATA\fP
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This is the same as the \%\f3GLU_NURBS_VERTEX\fP callback, except that
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it takes an additional pointer argument. This pointer is a copy of the
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pointer that was specified at the last call to
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\%\f3gluNurbsCallbackData\fP. The default callback function is NULL. The
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function prototype for this callback function looks like:
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.RS
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.Ex
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void vertexData ( GLfloat *vertex, void *userData );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_NORMAL\fP
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The normal callback is invoked as the vertex normal is generated.
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The components of the normal are stored in the parameter ``normal''.
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In the case of a NURBS curve, the callback function is effective only when
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the user provides a normal map (\%\f3GL_MAP1_NORMAL\fP).
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In the case of a NURBS surface, if a normal map (\%\f3GL_MAP2_NORMAL\fP) is provided, then the generated normal is computed from the normal map.
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If a normal map is not provided then a surface normal is computed in
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a manner similar to that described for evaluators when \%\f3GL_AUTO_NORMAL\fP
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is enabled.
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.bp
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The default normal callback function is NULL. The function
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prototype for this callback function looks like:
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.RS
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.Ex
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void normal ( GLfloat *normal );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_NORMAL_DATA\fP
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The same as the \%\f3GLU_NURBS_NORMAL\fP callback except that it
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takes an additional pointer argument. This pointer is a copy of the pointer
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that was specified at the last call to \%\f3gluNurbsCallbackData\fP. The default callback function is NULL. The function prototype for this callback function looks like:
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.RS
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.Ex
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void normalData ( GLfloat *normal, void *userData );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_COLOR\fP
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The color callback is invoked as the color of a vertex is generated.
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The components of the color are stored in the parameter ``color''.
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This callback is effective only when the user provides a color map
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(\%\f3GL_MAP1_COLOR_4\fP or \%\f3GL_MAP2_COLOR_4\fP). ``color'' contains four components: R,G,B,A. The default color callback function is NULL. The prototype for
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this callback function looks like:
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.RS
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.Ex
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void color ( GLfloat *color );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_COLOR_DATA\fP
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The same as the \%\f3GLU_NURBS_COLOR\fP callback except that it
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takes an additional pointer argument. This pointer is a copy of the pointer
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that was specified at the last call to \%\f3gluNurbsCallbackData\fP. The default callback function is NULL. The function prototype for this callback function looks like:
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.RS
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.Ex
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void colorData ( GLfloat *color, void *userData );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_TEXTURE_COORD\fP
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The texture callback is invoked as the texture coordinates
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of a vertex are generated. These coordinates are stored in the parameter
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``texCoord''. The number of texture coordinates can be 1, 2, 3, or 4 depending
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on which type of texture map is specified
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(\%\f3GL_MAP1_TEXTURE_COORD_1\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_2\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_3\fP,
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\%\f3GL_MAP1_TEXTURE_COORD_4\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_1\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_2\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_3\fP,
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\%\f3GL_MAP2_TEXTURE_COORD_4\fP).
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If no texture map is specified, this callback function will not be called.
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.bp
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The default texture callback function is NULL. The function prototype
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for this callback function looks like:
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.RS
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.Ex
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void texCoord ( GLfloat *texCoord );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_TEXTURE_COORD_DATA\fP
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This is the same as the \%\f3GLU_NURBS_TEXTURE_COORD\fP callback, except that it
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takes an additional pointer argument. This pointer is a copy of the pointer
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that was specified at the last call to \%\f3gluNurbsCallbackData\fP. The default callback function is NULL. The function prototype for this callback function looks like:
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.RS
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.Ex
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void texCoordData (GLfloat *texCoord, void *userData);
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_END\fP
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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:
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.RS
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.Ex
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void end ( void );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_END_DATA\fP
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This is the same as the \%\f3GLU_NURBS_END\fP callback, except that it
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takes an additional pointer argument. This pointer is a copy of the pointer
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that was specified at the last call to \%\f3gluNurbsCallbackData\fP. The default callback function is NULL. The function prototype for this callback function looks like:
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.RS
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.Ex
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void endData ( void *userData );
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.Ee
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.RE
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.TP
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\%\f3GLU_NURBS_ERROR\fP
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The error function is called when an error is encountered.
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Its single argument
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is of type GLenum, and it indicates the specific error that occurred.
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There are 37 errors unique to NURBS named
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\%\f3GLU_NURBS_ERROR1\fP through \%\f3GLU_NURBS_ERROR37\fP.
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Character strings describing these errors can be retrieved with
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\%\f3gluErrorString\fP.
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.bp
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.SH NOTES
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\%\f3gluNurbsCallback\fP is available only if the GLU version is 1.2 or greater.
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.P
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GLU version 1.2 supports only the \%\f3GLU_ERROR\fP parameter for
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\f2which\fP. The \%\f3GLU_ERROR\fP value is deprecated in GLU version 1.3 in
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favor of \%\f3GLU_NURBS_ERROR\fP. All other accepted values for \f2CallBackFunc\fP
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are available only if the GLU version is 1.3 or greater.
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.SH SEE ALSO
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\%\f3gluErrorString(3G)\fP,
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\%\f3gluNewNurbsRenderer(3G)\fP,
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\%\f3gluNurbsCallbackData(3G)\fP,
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\%\f3gluNurbsProperty(3G)\fP
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