<div class="refentry" id="glClipControl">

<div class="titlepage"></div>

<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"><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"><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="https://www.opengl.org/registry/" target="_top">https://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>

{$pipelinestall}{$examples}

<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"><span class="citerefentry"><span class="refentrytitle">gl_ClipDistance</span></span></a>,

<a class="citerefentry" href="gl_CullDistance"><span class="citerefentry"><span class="refentrytitle">gl_CullDistance</span></span></a>,

<a class="citerefentry" href="gl_FrontFacing"><span class="citerefentry"><span class="refentrytitle">gl_FrontFacing</span></span></a>,

<a class="citerefentry" href="glDepthRange"><span class="citerefentry"><span class="refentrytitle">glDepthRange</span></span></a>.

</p>

</div>

<div class="refsect1" id="Copyright">

<h2>Copyright</h2>

<p>

Copyright © 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="https://opencontent.org/openpub/" target="_top">https://opencontent.org/openpub/</a>.

</p>

</div>

</div>