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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>gluTessProperty</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="gluTessProperty"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>gluTessProperty — set a tessellation object property</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">gluTessProperty</b>(</code></td><td>GLUtesselator* </td><td><var class="pdparam">tess</var>, </td></tr><tr><td> </td><td>GLenum </td><td><var class="pdparam">which</var>, </td></tr><tr><td> </td><td>GLdouble </td><td><var class="pdparam">data</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>
+ Specifies the tessellation object (created with <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</span></span></a>).
+ </p></dd><dt><span class="term"><em class="parameter"><code>which</code></em></span></dt><dd><p>
+ Specifies the property to be set. Valid values are
+ <code class="constant">GLU_TESS_WINDING_RULE</code>,
+ <code class="constant">GLU_TESS_BOUNDARY_ONLY</code>, and
+ <code class="constant">GLU_TESS_TOLERANCE</code>.
+ </p></dd><dt><span class="term"><em class="parameter"><code>data</code></em></span></dt><dd><p>
+ Specifies the value of the indicated property.
+ </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
+ <code class="function">gluTessProperty</code> is used to control properties stored in a tessellation object. These
+ properties affect the way that the polygons are interpreted and rendered.
+ The legal values for <em class="parameter"><code>which</code></em> are as follows:
+ </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GLU_TESS_WINDING_RULE</code> </span></dt><dd><p>
+ Determines which parts of the polygon are on the ``interior''.
+ <em class="parameter"><code>data</code></em> may be set to one of <code class="constant">GLU_TESS_WINDING_ODD</code>,
+ <code class="constant">GLU_TESS_WINDING_NONZERO</code>, <code class="constant">GLU_TESS_WINDING_POSITIVE</code>,
+ <code class="constant">GLU_TESS_WINDING_NEGATIVE</code>, or <code class="constant">GLU_TESS_WINDING_ABS_GEQ_TWO</code>.
+ </p><p>
+ To understand how the winding rule works, consider that the input
+ contours partition the plane into regions. The winding rule determines which
+ of these regions are inside the polygon.
+ </p><p>
+ For a single contour C, the winding number of a point x is simply the signed
+ number of revolutions we make around x as we travel once around C
+ (where CCW is positive). When there are several contours, the individual
+ winding numbers are summed. This procedure associates a signed integer
+ value with each point x in the plane. Note that the winding number is the
+ same for all points in a single region.
+ </p><p>
+ The winding rule classifies a region as ``inside'' if its winding number
+ belongs to the chosen category (odd, nonzero, positive, negative, or
+ absolute value of at least two). The previous GLU tessellator (prior to
+ GLU 1.2) used the ``odd'' rule. The ``nonzero'' rule is another common way to
+ define the interior. The other three rules are useful for polygon CSG
+ operations.
+ </p></dd><dt><span class="term"><code class="constant">GLU_TESS_BOUNDARY_ONLY</code> </span></dt><dd><p>
+ Is a boolean value (``value'' should be set
+ to GL_TRUE or GL_FALSE). When set to GL_TRUE, a set of closed contours
+ separating the polygon interior and exterior are returned instead of a
+ tessellation. Exterior contours are oriented CCW with respect to the
+ normal; interior contours are oriented CW. The <code class="constant">GLU_TESS_BEGIN</code>
+ and <code class="constant">GLU_TESS_BEGIN_DATA</code> callbacks use the type GL_LINE_LOOP for
+ each contour.
+ </p></dd><dt><span class="term"><code class="constant">GLU_TESS_TOLERANCE</code></span></dt><dd><p>
+ Specifies a tolerance for merging features to reduce the size of the output.
+ For example, two vertices that are very close to each other might be
+ replaced by a single vertex. The tolerance is multiplied by the largest
+ coordinate magnitude of any input vertex; this specifies the maximum
+ distance that any feature can move as the result of a single merge
+ operation. If a single feature takes part in several merge operations, the
+ total distance moved could be larger.
+ </p><p>
+ Feature merging is completely optional; the tolerance is only a hint.
+ The implementation is free to merge in some cases and not in others, or to
+ never merge features at all. The initial tolerance is 0.
+ </p><p>
+ The current implementation merges vertices only if they are exactly
+ coincident, regardless of the current tolerance. A vertex is spliced into
+ an edge only if the implementation is unable to distinguish which side of
+ the edge the vertex lies on. Two edges are merged only when both endpoints
+ are identical.
+ </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
+ <a class="citerefentry" href="gluGetTessProperty.xml"><span class="citerefentry"><span class="refentrytitle">gluGetTessProperty</span></span></a>,
+ <a class="citerefentry" href="gluNewTess.xml"><span class="citerefentry"><span class="refentrytitle">gluNewTess</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>
HCoop / clinton / guile-figl.git / blobdiff