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+<?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>gluNurbsCallback</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluNurbsCallback"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluNurbsCallback — define a callback for a NURBS object</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">gluNurbsCallback</b>(</code></td><td>GLUnurbs* </td><td><var class="pdparam">nurb</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">which</var>, </td></tr><tr><td> </td><td>_GLUfuncptr </td><td><var class="pdparam">CallBackFunc</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>nurb</code></em></span></dt><dd><p>
+ Specifies the NURBS object (created with <a class="citerefentry" href="gluNewNurbsRenderer.xml"><span class="citerefentry"><span class="refentrytitle">gluNewNurbsRenderer</span></span></a>).
+ </p></dd><dt><span class="term"><em class="parameter"><code>which</code></em></span></dt><dd><p>
+ Specifies the callback being defined.
+ Valid values are <code class="constant">GLU_NURBS_BEGIN</code>, <code class="constant">GLU_NURBS_VERTEX</code>, <code class="constant">GLU_NURBS_NORMAL</code>, <code class="constant">GLU_NURBS_COLOR</code>, <code class="constant">GLU_NURBS_TEXTURE_COORD</code>, <code class="constant">GLU_NURBS_END</code>, <code class="constant">GLU_NURBS_BEGIN_DATA</code>, <code class="constant">GLU_NURBS_VERTEX_DATA</code>, <code class="constant">GLU_NURBS_NORMAL_DATA</code>, <code class="constant">GLU_NURBS_COLOR_DATA</code>, <code class="constant">GLU_NURBS_TEXTURE_COORD_DATA</code>, <code class="constant">GLU_NURBS_END_DATA</code>, and <code class="constant">GLU_NURBS_ERROR</code>.
+ </p></dd><dt><span class="term"><em class="parameter"><code>CallBackFunc</code></em></span></dt><dd><p>
+ Specifies the function that the callback calls.
+ </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
+ <code class="function">gluNurbsCallback</code> 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
+ <em class="parameter"><code>CallBackFunc</code></em> is NULL, then this callback will not get
+ invoked and the related data, if any, will be lost.
+ </p><p>
+ Except the error callback, these callbacks are used by NURBS tessellator (when <code class="constant">GLU_NURBS_MODE</code> is set to be <code class="constant">GLU_NURBS_TESSELLATOR</code>) 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 <code class="function">gluNurbsCallbackData</code>.
+ </p><p>
+ The error callback function is effective no matter which value that
+ <code class="constant">GLU_NURBS_MODE</code> is set to.
+ All other callback functions are effective only when <code class="constant">GLU_NURBS_MODE</code>
+ is set to <code class="constant">GLU_NURBS_TESSELLATOR</code>.
+ </p><p>
+ The legal callbacks are as follows:
+ </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLU_NURBS_BEGIN</code></span></dt><dd><p>
+ </p><p>
+ The begin callback indicates the start of a primitive. The function
+ takes a single argument of type GLenum, which can be one of
+ <code class="constant">GLU_LINES</code>, <code class="constant">GLU_LINE_STRIP</code>, <code class="constant">GLU_TRIANGLE_FAN</code>, <code class="constant">GLU_TRIANGLE_STRIP</code>, <code class="constant">GLU_TRIANGLES</code>, or <code class="constant">GLU_QUAD_STRIP</code>. The
+ default begin callback function is NULL. The function prototype
+ for this callback looks like:
+ </p><pre class="programlisting">
+void begin( GLenum type );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_BEGIN_DATA</code></span></dt><dd><p>
+ </p><p>
+ The same as the <code class="constant">GLU_NURBS_BEGIN</code> 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 <code class="function">gluNurbsCallbackData</code>. The
+ default callback function is NULL. The function prototype for this
+ callback function looks like:
+ </p><pre class="programlisting">
+void beginData(GLenum type, void *userData);
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_VERTEX</code></span></dt><dd><p>
+ </p><p>
+ 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:
+ </p><pre class="programlisting">
+void vertex( GLfloat *vertex );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_VERTEX_DATA</code></span></dt><dd><p>
+ </p><p>
+ This is the same as the <code class="constant">GLU_NURBS_VERTEX</code> 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
+ <code class="function">gluNurbsCallbackData</code>. The default callback function is NULL. The
+ function prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void vertexData( GLfloat *vertex, void *userData );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_NORMAL</code></span></dt><dd><p>
+ </p><p>
+ 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 (<code class="constant">GLU_MAP1_NORMAL</code>).
+ In the case of a NURBS surface, if a normal map (<code class="constant">GLU_MAP2_NORMAL</code>)
+ 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 <code class="constant">GLU_AUTO_NORMAL</code>
+ is enabled.
+ The default normal callback function is NULL. The function
+ prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void normal( GLfloat *normal );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_NORMAL_DATA</code></span></dt><dd><p>
+ </p><p>
+ The same as the <code class="constant">GLU_NURBS_NORMAL</code> 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 <code class="function">gluNurbsCallbackData</code>. The default callback function is NULL. The function prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void normalData( GLfloat *normal, void *userData );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_COLOR</code></span></dt><dd><p>
+ </p><p>
+ 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
+ (<code class="constant">GLU_MAP1_COLOR_4</code> or <code class="constant">GLU_MAP2_COLOR_4</code>). ``color'' contains four
+ components: R, G, B, A. The default color callback function is NULL.
+ The prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void color( GLfloat *color );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_COLOR_DATA</code></span></dt><dd><p>
+ </p><p>
+ The same as the <code class="constant">GLU_NURBS_COLOR</code> 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 <code class="function">gluNurbsCallbackData</code>. The default callback function is NULL. The function prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void colorData( GLfloat *color, void *userData );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_TEXTURE_COORD</code></span></dt><dd><p>
+ </p><p>
+ 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
+ (<code class="constant">GLU_MAP1_TEXTURE_COORD_1</code>,
+ <code class="constant">GLU_MAP1_TEXTURE_COORD_2</code>,
+ <code class="constant">GLU_MAP1_TEXTURE_COORD_3</code>,
+ <code class="constant">GLU_MAP1_TEXTURE_COORD_4</code>,
+ <code class="constant">GLU_MAP2_TEXTURE_COORD_1</code>,
+ <code class="constant">GLU_MAP2_TEXTURE_COORD_2</code>,
+ <code class="constant">GLU_MAP2_TEXTURE_COORD_3</code>,
+ <code class="constant">GLU_MAP2_TEXTURE_COORD_4</code>).
+ 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:
+ </p><pre class="programlisting">
+void texCoord( GLfloat *texCoord );
+ </pre><p>
+ </p></dd><dt><span class="term"> <code class="constant">GLU_NURBS_TEXTURE_COORD_DATA</code></span></dt><dd><p>
+ </p><p>
+ This is the same as the <code class="constant">GLU_NURBS_TEXTURE_COORD</code> 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 <code class="function">gluNurbsCallbackData</code>. The default callback function is NULL. The function prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void texCoordData( GLfloat *texCoord, void *userData );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_END</code></span></dt><dd><p>
+ </p><p>
+ 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:
+ </p><pre class="programlisting">
+void end( void );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_END_DATA</code></span></dt><dd><p>
+ </p><p>
+ This is the same as the <code class="constant">GLU_NURBS_END</code> 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 <code class="function">gluNurbsCallbackData</code>. The default callback function is NULL. The function prototype for this callback function looks like:
+ </p><pre class="programlisting">
+void endData( void *userData );
+ </pre><p>
+ </p></dd><dt><span class="term"><code class="constant">GLU_NURBS_ERROR</code></span></dt><dd><p>
+ </p><p>
+ 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
+ <code class="constant">GLU_NURBS_ERROR1</code> through <code class="constant">GLU_NURBS_ERROR37</code>.
+ Character strings describing these errors can be retrieved with
+ <a class="citerefentry" href="gluErrorString.xml"><span class="citerefentry"><span class="refentrytitle">gluErrorString</span></span></a>.
+ </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
+ <code class="function">gluNurbsCallback</code> is available only if the GLU version is 1.2 or greater.
+ </p><p>
+ GLU version 1.2 supports only the <code class="constant">GLU_ERROR</code> parameter for
+ <em class="parameter"><code>which</code></em>. The <code class="constant">GLU_ERROR</code> value is deprecated in GLU version 1.3 in
+ favor of <code class="constant">GLU_NURBS_ERROR</code>. All other accepted values for <em class="parameter"><code>CallBackFunc</code></em>
+ are available only if the GLU version is 1.3 or greater.
+ </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
+ <a class="citerefentry" href="gluErrorString.xml"><span class="citerefentry"><span class="refentrytitle">gluErrorString</span></span></a>,
+ <a class="citerefentry" href="gluNewNurbsRenderer.xml"><span class="citerefentry"><span class="refentrytitle">gluNewNurbsRenderer</span></span></a>,
+ <code class="function">gluNurbsCallbackData</code>,
+ <a class="citerefentry" href="gluNurbsProperty.xml"><span class="citerefentry"><span class="refentrytitle">gluNurbsProperty</span></span></a>
+ </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
+ Copyright <span class="trademark"></span>© 1991-2006
+ Silicon Graphics, Inc. This document is licensed under the SGI
+ Free Software B License. For details, see
+ <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
+ </p></div></div></body></html>
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