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1 | <?xml version="1.0" encoding="UTF-8"?> |
2 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> | |
3 | <!-- saved from url=(0013)about:internet --> | |
4 | <?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" /><link rel="stylesheet" type="text/css" href="opengl-man.css" /><title>glLineWidth - OpenGL 4 Reference Pages</title><meta name="generator" content="DocBook XSL Stylesheets V1.69.1" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glLineWidth"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glLineWidth — specify the width of rasterized lines</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><p><code class="funcdef">void <b class="fsfunc">glLineWidth</b>(</code>GLfloat <var class="pdparam">width</var><code>)</code>;</p></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>width</code></em></span></dt><dd><p> | |
5 | Specifies the width of rasterized lines. | |
6 | The initial value is 1. | |
7 | </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p> | |
8 | <code class="function">glLineWidth</code> specifies the rasterized width of both aliased and antialiased | |
9 | lines. | |
10 | Using a line width other than 1 has different effects, | |
11 | depending on whether line antialiasing is enabled. | |
12 | To enable and disable line antialiasing, call | |
13 | <a href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and <a href="glDisable.xml"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a> | |
14 | with argument <code class="constant">GL_LINE_SMOOTH</code>. Line antialiasing is initially | |
15 | disabled. | |
16 | </p><p> | |
17 | If line antialiasing is disabled, | |
18 | the actual width is determined by rounding the supplied width | |
19 | to the nearest integer. | |
20 | (If the rounding results in the value 0, | |
21 | it is as if the line width were 1.) | |
22 | If | |
23 | <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> | |
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28 | <mml:mo>Δ</mml:mo> | |
29 | <mml:mi mathvariant="italic">x</mml:mi> | |
30 | </mml:mrow> | |
31 | </mml:mfenced> | |
32 | <mml:mo>>=</mml:mo> | |
33 | <mml:mfenced open="∣" close="∣"> | |
34 | <mml:mrow> | |
35 | <mml:mo>Δ</mml:mo> | |
36 | <mml:mi mathvariant="italic">y</mml:mi> | |
37 | </mml:mrow> | |
38 | </mml:mfenced> | |
39 | </mml:mrow> | |
40 | </mml:math>, | |
41 | <span class="emphasis"><em>i</em></span> pixels are filled in each column that is rasterized, | |
42 | where <span class="emphasis"><em>i</em></span> is the rounded value of <em class="parameter"><code>width</code></em>. | |
43 | Otherwise, | |
44 | <span class="emphasis"><em>i</em></span> pixels are filled in each row that is rasterized. | |
45 | </p><p> | |
46 | If antialiasing is enabled, | |
47 | line rasterization produces a fragment for each pixel square | |
48 | that intersects the region lying within the rectangle having width | |
49 | equal to the current line width, | |
50 | length equal to the actual length of the line, | |
51 | and centered on the mathematical line segment. | |
52 | The coverage value for each fragment is the window coordinate area | |
53 | of the intersection of the rectangular region with the corresponding | |
54 | pixel square. | |
55 | This value is saved and used in the final rasterization step. | |
56 | </p><p> | |
57 | Not all widths can be supported when line antialiasing is enabled. If an | |
58 | unsupported width is requested, the nearest supported width is used. | |
59 | Only width 1 is guaranteed to be supported; others depend on the | |
60 | implementation. Likewise, there is a range for aliased line widths as well. | |
61 | To query the range of supported widths and the size | |
62 | difference between supported widths within the range, call <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> | |
63 | with arguments <code class="constant">GL_ALIASED_LINE_WIDTH_RANGE</code>, | |
64 | <code class="constant">GL_SMOOTH_LINE_WIDTH_RANGE</code>, and <code class="constant">GL_SMOOTH_LINE_WIDTH_GRANULARITY</code>. | |
65 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p> | |
66 | The line width specified by <code class="function">glLineWidth</code> is always returned when <code class="constant">GL_LINE_WIDTH</code> | |
67 | is queried. | |
68 | Clamping and rounding for aliased and antialiased lines have no effect on the specified value. | |
69 | </p><p> | |
70 | Nonantialiased line width may be clamped to an implementation-dependent maximum. Call <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with <code class="constant">GL_ALIASED_LINE_WIDTH_RANGE</code> to determine the maximum width. | |
71 | </p><p> | |
72 | In OpenGL 1.2, the tokens <code class="constant">GL_LINE_WIDTH_RANGE</code> and <code class="constant">GL_LINE_WIDTH_GRANULARITY</code> were replaced by <code class="constant">GL_ALIASED_LINE_WIDTH_RANGE</code>, | |
73 | <code class="constant">GL_SMOOTH_LINE_WIDTH_RANGE</code>, and <code class="constant">GL_SMOOTH_LINE_WIDTH_GRANULARITY</code>. The old names are retained for backward compatibility, but should not be used in new code. | |
74 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p> | |
75 | <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>width</code></em> is less than or equal to 0. | |
76 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p> | |
77 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_LINE_WIDTH</code> | |
78 | </p><p> | |
79 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_ALIASED_LINE_WIDTH_RANGE</code> | |
80 | </p><p> | |
81 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SMOOTH_LINE_WIDTH_RANGE</code> | |
82 | </p><p> | |
83 | <a href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_SMOOTH_LINE_WIDTH_GRANULARITY</code> | |
84 | </p><p> | |
85 | <a href="glIsEnabled.xml"><span class="citerefentry"><span class="refentrytitle">glIsEnabled</span></span></a> with argument <code class="constant">GL_LINE_SMOOTH</code> | |
86 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p> | |
87 | <a href="glEnable.xml"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> | |
88 | </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p> | |
89 | Copyright <span class="trademark"></span>© 1991-2006 | |
90 | Silicon Graphics, Inc. This document is licensed under the SGI | |
91 | Free Software B License. For details, see | |
92 | <a href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>. | |
93 | </p></div></div></body></html> |