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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html><html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>glClipControl - OpenGL 4 Reference Pages</title>
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<header/>
<div class="refentry" id="glClipControl">
<div class="titlepage"/>
<div class="refnamediv">
<h2>Name</h2>
<p>glClipControl — control clip coordinate to window coordinate behavior</p>
</div>
<div class="refsynopsisdiv">
<h2>C Specification</h2>
<div class="funcsynopsis">
<table style="border: 0; cellspacing: 0; cellpadding: 0;" class="funcprototype-table">
<tr>
<td>
<code class="funcdef">void <strong class="fsfunc">glClipControl</strong>(</code>
</td>
<td>GLenum <var class="pdparam">origin</var>, </td>
</tr>
<tr>
<td> </td>
<td>GLenum <var class="pdparam">depth</var><code>)</code>;</td>
</tr>
</table>
<div class="funcprototype-spacer"> </div>
</div>
</div>
<div class="refsect1" id="parameters">
<h2>Parameters</h2>
<div class="variablelist">
<dl class="variablelist">
<dt>
<span class="term">
<em class="parameter">
<code>origin</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the clip control origin. Must be one of
<code class="constant">GL_LOWER_LEFT</code> or
<code class="constant">GL_UPPER_LEFT</code>.
</p>
</dd>
<dt>
<span class="term">
<em class="parameter">
<code>depth</code>
</em>
</span>
</dt>
<dd>
<p>
Specifies the clip control depth mode. Must be one
of <code class="constant">GL_NEGATIVE_ONE_TO_ONE</code> or
<code class="constant">GL_ZERO_TO_ONE</code>.
</p>
</dd>
</dl>
</div>
</div>
<div class="refsect1" id="description">
<h2>Description</h2>
<p>
<code class="function">glClipControl</code> controls the clipping volume
behavior and the clip coordinate to window coordinate
transformation behavior.
</p>
<p>
The view volume is defined by
$$z_{min} \leq z_c \leq w_c$$
where $z_{min} = -w_c$ when <em class="parameter"><code>depth</code></em> is
<code class="constant">GL_NEGATIVE_ONE_TO_ONE</code>, and $z_{min} = 0$
when <em class="parameter"><code>depth</code></em> is
<code class="constant">GL_ZERO_TO_ONE</code>.
</p>
<p>
The normalized device coordinate $y_d$ is given by
$$y_d = { { f \times y_c } \over w_c }$$
where $f = 1$ when <em class="parameter"><code>origin</code></em> is
<code class="constant">GL_LOWER_LEFT</code>, and $f = -1$ when
<em class="parameter"><code>origin</code></em> is
<code class="constant">GL_UPPER_LEFT</code>.
</p>
<p>
The window coordinate $z_w$ is given by
$$z_w = s \times z_d + b$$
where $s = { { f - n } \over 2 }$ and $b = { {n + f} \over 2 }$ when
<em class="parameter"><code>depth</code></em> is
<code class="constant">GL_NEGATIVE_ONE_TO_ONE</code>, and $s = f - n$ and
$b = n$ when <em class="parameter"><code>depth</code></em> is
<code class="constant">GL_ZERO_TO_ONE</code>. $n$ and $f$ are the near
and far depth range values set with
<a class="citerefentry" href="glDepthRange.xhtml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>.
</p>
<p>
Finally, the polygon area computation defined by
<a class="citerefentry" href="gl_FrontFacing.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_FrontFacing</span></span></a>
to determine if a polygon is front- or back-facing has its sign
negated when <em class="parameter"><code>origin</code></em> is
<code class="constant">GL_UPPER_LEFT</code>.
</p>
</div>
<div class="refsect1" id="notes">
<h2>Notes</h2>
<p>
The default GL clip volume definition is for a
<em class="parameter"><code>origin</code></em> of
<code class="constant">GL_LOWER_LEFT</code> and a
<em class="parameter"><code>depth</code></em> of
<code class="constant">GL_NEGATIVE_ONE_TO_ONE</code>.
</p>
<p>
An <em class="parameter"><code>origin</code></em> of
<code class="constant">GL_UPPER_LEFT</code> and a
<em class="parameter"><code>depth</code></em> of
<code class="constant">GL_ZERO_TO_ONE</code> corresponds to Direct3D's
clip volume definition.
</p>
<p>
An <em class="parameter"><code>origin</code></em> of
<code class="constant">GL_UPPER_LEFT</code> and a
<em class="parameter"><code>depth</code></em> of
<code class="constant">GL_NEGATIVE_ONE_TO_ONE</code> corresponds to the
upper-left origin of the window coordinate system of Microsoft
Windows and the X Window System.
</p>
<p>
There is extensive discussion of the uses and further
consequences of the different clip volume settings in the
<code class="code">GL_ARB_clip_control</code> extension specification in the
OpenGL Registry at URL <a class="link" href="http://www.opengl.org/registry/" target="_top">http://www.opengl.org/registry/</a>.
</p>
</div>
<div class="refsect1" id="errors">
<h2>Errors</h2>
<p>
An <code class="constant">GL_INVALID_ENUM</code> error is generated if
<em class="parameter"><code>origin</code></em> is not
<code class="constant">GL_LOWER_LEFT</code> or
<code class="constant">GL_UPPER_LEFT</code>.
</p>
<p>
An <code class="constant">GL_INVALID_ENUM</code> error is generated if
<em class="parameter"><code>depth</code></em> is not
<code class="constant">GL_NEGATIVE_ONE_TO_ONE</code> or
<code class="constant">GL_ZERO_TO_ONE</code>.
</p>
</div>
<div class="refsect1" id="versions">
<h2>Version Support</h2>
<div class="informaltable">
<table style="border-collapse: collapse; border-top: 2px solid ; border-bottom: 2px solid ; border-left: 2px solid ; border-right: 2px solid ; ">
<colgroup>
<col style="text-align: left; "/>
<col style="text-align: center; " class="firstvers"/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; "/>
<col style="text-align: center; " class="lastvers"/>
</colgroup>
<thead>
<tr>
<th style="text-align: left; border-right: 2px solid ; ">
</th>
<th style="text-align: center; border-bottom: 2px solid ; " colspan="12">
<span class="bold"><strong>OpenGL Version</strong></span>
</th>
</tr>
<tr>
<th style="text-align: left; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>Function / Feature Name</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>2.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>3.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.0</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.1</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.2</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.3</strong></span>
</th>
<th style="text-align: center; border-right: 2px solid ; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.4</strong></span>
</th>
<th style="text-align: center; border-bottom: 2px solid ; ">
<span class="bold"><strong>4.5</strong></span>
</th>
</tr>
</thead>
<tbody>
<tr>
<td style="text-align: left; border-right: 2px solid ; ">
<code class="function">glClipControl</code>
</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; border-right: 2px solid ; ">-</td>
<td style="text-align: center; ">✔</td>
</tr>
</tbody>
</table>
</div>
</div>
<div class="refsect1" id="seealso">
<h2>See Also</h2>
<p>
<a class="citerefentry" href="gl_ClipDistance.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_ClipDistance</span></span></a>,
<a class="citerefentry" href="gl_CullDistance.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_CullDistance</span></span></a>,
<a class="citerefentry" href="gl_FrontFacing.xhtml"><span class="citerefentry"><span class="refentrytitle">gl_FrontFacing</span></span></a>,
<a class="citerefentry" href="glDepthRange.xhtml"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>.
</p>
</div>
<div class="refsect1" id="Copyright">
<h2>Copyright</h2>
<p>
Copyright <span class="trademark"/>© 2014 Khronos Group.
This material may be distributed subject to the terms and conditions set forth in
the Open Publication License, v 1.0, 8 June 1999.
<a class="link" href="http://opencontent.org/openpub/" target="_top">http://opencontent.org/openpub/</a>.
</p>
</div>
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