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"1.0" encoding=
"UTF-8"?>
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pref=
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renderer=
"mathplayer-dl"><head><meta http-equiv=
"Content-Type" content=
"text/html; charset=UTF-8" /><link rel=
"stylesheet" type=
"text/css" href=
"opengl-man.css" /><title>glPolygonOffset
</title><meta name=
"generator" content=
"DocBook XSL Stylesheets V1.69.1" /></head><body><div class=
"refentry" lang=
"en" xml:
lang=
"en"><a id=
"glPolygonOffset"></a><div class=
"titlepage"></div><div class=
"refnamediv"><h2>Name
</h2><p>glPolygonOffset — set the scale and units used to calculate depth values
</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">glPolygonOffset
</b>(
</code></td><td>GLfloat
</td><td><var class=
"pdparam">factor
</var>,
</td></tr><tr><td> </td><td>GLfloat
</td><td><var class=
"pdparam">units
</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>factor
</code></em></span></dt><dd><p>
5 Specifies a scale factor that is used to create a variable
6 depth offset for each polygon. The initial value is
0.
7 </p></dd><dt><span class=
"term"><em class=
"parameter"><code>units
</code></em></span></dt><dd><p>
8 Is multiplied by an implementation-specific value to
9 create a constant depth offset. The initial value is
0.
10 </p></dd></dl></div></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"description"></a><h2>Description
</h2><p>
11 When
<code class=
"constant">GL_POLYGON_OFFSET_FILL
</code>,
<code class=
"constant">GL_POLYGON_OFFSET_LINE
</code>, or
12 <code class=
"constant">GL_POLYGON_OFFSET_POINT
</code> is enabled, each
13 fragment's
<span class=
"emphasis"><em>depth
</em></span> value will be offset after it is interpolated
14 from the
<span class=
"emphasis"><em>depth
</em></span> values of the appropriate vertices.
15 The value of the offset is
16 <mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
20 <mml:mi mathvariant=
"italic">factor
</mml:mi>
22 <mml:mi mathvariant=
"italic">DZ
</mml:mi>
26 <mml:mi mathvariant=
"italic">r
</mml:mi>
28 <mml:mi mathvariant=
"italic">units
</mml:mi>
33 <mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll">
35 <mml:mi mathvariant=
"italic">DZ
</mml:mi>
37 is a measurement of the change in depth relative to the screen
38 area of the polygon, and
39 <mml:math xmlns:
mml=
"http://www.w3.org/1998/Math/MathML" overflow=
"scroll"><mml:mi mathvariant=
"italic">r
</mml:mi></mml:math>
40 is the smallest value that is guaranteed to
41 produce a resolvable offset for a given implementation.
42 The offset is added before the depth test is performed and before
43 the value is written into the depth buffer.
45 <code class=
"function">glPolygonOffset
</code> is useful for rendering hidden-line images, for applying decals
46 to surfaces, and for rendering solids with highlighted edges.
47 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"associatedgets"></a><h2>Associated Gets
</h2><p>
48 <a href=
"glIsEnabled.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glIsEnabled
</span></span></a> with argument
49 <code class=
"constant">GL_POLYGON_OFFSET_FILL
</code>,
50 <code class=
"constant">GL_POLYGON_OFFSET_LINE
</code>,
51 or
<code class=
"constant">GL_POLYGON_OFFSET_POINT
</code>.
53 <a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a> with argument
<code class=
"constant">GL_POLYGON_OFFSET_FACTOR
</code> or
54 <code class=
"constant">GL_POLYGON_OFFSET_UNITS
</code>.
55 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"seealso"></a><h2>See Also
</h2><p>
56 <a href=
"glDepthFunc.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glDepthFunc
</span></span></a>,
57 <a href=
"glEnable.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glEnable
</span></span></a>,
58 <a href=
"glGet.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glGet
</span></span></a>,
59 <a href=
"glIsEnabled.xml"><span class=
"citerefentry"><span class=
"refentrytitle">glIsEnabled
</span></span></a>
60 </p></div><div class=
"refsect1" lang=
"en" xml:
lang=
"en"><a id=
"Copyright"></a><h2>Copyright
</h2><p>
61 Copyright
<span class=
"trademark"></span>©
1991-
2006
62 Silicon Graphics, Inc. This document is licensed under the SGI
63 Free Software B License. For details, see
64 <a href=
"http://oss.sgi.com/projects/FreeB/" target=
"_top">http://oss.sgi.com/projects/FreeB/
</a>.
65 </p></div></div></body></html>