| 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> |
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| 3 | <?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>gluNextContour</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluNextContour"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluNextContour — mark the beginning of another contour</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">gluNextContour</b>(</code></td><td>GLUtesselator* </td><td><var class="pdparam">tess</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">type</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>tess</code></em></span></dt><dd><p> |
| 4 | Specifies the tessellation object (created with <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</span></span></a>). |
| 5 | </p></dd><dt><span class="term"><em class="parameter"><code>type</code></em></span></dt><dd><p> |
| 6 | Specifies the type of the contour being defined. Valid values are |
| 7 | <code class="constant">GLU_EXTERIOR</code>, |
| 8 | <code class="constant">GLU_INTERIOR</code>, |
| 9 | <code class="constant">GLU_UNKNOWN</code>, |
| 10 | <code class="constant">GLU_CCW</code>, and |
| 11 | <code class="constant">GLU_CW</code>. |
| 12 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> |
| 13 | <code class="function">gluNextContour</code> is used in describing polygons with multiple contours. After the first |
| 14 | contour has been described through a series of <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a> calls, |
| 15 | a <code class="function">gluNextContour</code> call indicates that the previous contour is complete and that the |
| 16 | next contour is about to begin. |
| 17 | Another series of <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a> calls is then used to describe the new |
| 18 | contour. This process can be repeated until all contours have been described. |
| 19 | </p><p> |
| 20 | <em class="parameter"><code>type</code></em> defines what type of contour follows. |
| 21 | The legal contour types are as follows: |
| 22 | </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLU_EXTERIOR</code></span></dt><dd><p> |
| 23 | An exterior contour defines an exterior boundary of the polygon. |
| 24 | </p></dd><dt><span class="term"><code class="constant">GLU_INTERIOR</code></span></dt><dd><p> |
| 25 | An interior contour defines an interior boundary of the polygon (such as |
| 26 | a hole). |
| 27 | </p></dd><dt><span class="term"><code class="constant">GLU_UNKNOWN</code></span></dt><dd><p> |
| 28 | An unknown contour is analyzed by the library to determine if it is interior |
| 29 | or exterior. |
| 30 | </p></dd><dt><span class="term"><code class="constant">GLU_CCW</code>, </span></dt><dd></dd><dt><span class="term"><code class="constant">GLU_CW</code></span></dt><dd><p> |
| 31 | The first <code class="constant">GLU_CCW</code> or <code class="constant">GLU_CW</code> contour defined is considered to |
| 32 | be exterior. All other contours are considered to be exterior if they |
| 33 | are oriented in the same direction (clockwise or counterclockwise) as |
| 34 | the first contour, and interior if they are not. |
| 35 | </p></dd></dl></div><p> |
| 36 | If one contour is of type <code class="constant">GLU_CCW</code> or <code class="constant">GLU_CW</code>, then all |
| 37 | contours must be of the same type (if they are not, then all <code class="constant">GLU_CCW</code> |
| 38 | and <code class="constant">GLU_CW</code> contours will be changed to <code class="constant">GLU_UNKNOWN</code>). |
| 39 | </p><p> |
| 40 | Note that there is no real difference between the <code class="constant">GLU_CCW</code> and |
| 41 | <code class="constant">GLU_CW</code> contour types. |
| 42 | </p><p> |
| 43 | Before the first contour is described, <code class="function">gluNextContour</code> can be called to |
| 44 | define the type of the first contour. |
| 45 | If <code class="function">gluNextContour</code> is not called before the first contour, then the first contour is |
| 46 | marked <code class="constant">GLU_EXTERIOR</code>. |
| 47 | </p><p> |
| 48 | This command is obsolete and is provided for backward compatibility |
| 49 | only. Calls to <code class="function">gluNextContour</code> are mapped to <a class="citerefentry" href="gluTessEndContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessEndContour</span></span></a> |
| 50 | followed by |
| 51 | <a class="citerefentry" href="gluTessBeginContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessBeginContour</span></span></a>. |
| 52 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="example"></a><h2>Example</h2><p> |
| 53 | A quadrilateral with a triangular hole in it can be described as follows: |
| 54 | </p><pre class="programlisting"> |
| 55 | gluBeginPolygon(tobj); |
| 56 | gluTessVertex(tobj, v1, v1); |
| 57 | gluTessVertex(tobj, v2, v2); |
| 58 | gluTessVertex(tobj, v3, v3); |
| 59 | gluTessVertex(tobj, v4, v4); |
| 60 | gluNextContour(tobj, GLU_INTERIOR); |
| 61 | gluTessVertex(tobj, v5, v5); |
| 62 | gluTessVertex(tobj, v6, v6); |
| 63 | gluTessVertex(tobj, v7, v7); |
| 64 | gluEndPolygon(tobj); |
| 65 | </pre><p> |
| 66 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> |
| 67 | <a class="citerefentry" href="gluBeginPolygon.xml"><span class="citerefentry"><span class="refentrytitle">gluBeginPolygon</span></span></a>, |
| 68 | <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</span></span></a>, |
| 69 | <a class="citerefentry" href="gluTessBeginContour.xml"><span class="citerefentry"><span class="refentrytitle">gluTessBeginContour</span></span></a>, |
| 70 | <a class="citerefentry" href="gluTessCallback.xml"><span class="citerefentry"><span class="refentrytitle">gluTessCallback</span></span></a>, |
| 71 | <a class="citerefentry" href="gluTessVertex.xml"><span class="citerefentry"><span class="refentrytitle">gluTessVertex</span></span></a> |
| 72 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> |
| 73 | Copyright <span class="trademark"></span>© 1991-2006 |
| 74 | Silicon Graphics, Inc. This document is licensed under the SGI |
| 75 | Free Software B License. For details, see |
| 76 | <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. |
| 77 | </p></div></div></body></html> |