<div class="refentry" title="glScissor"><a id="glScissor"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glScissor — define the scissor box</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glScissor</b>(</code></td><td>GLint <var class="pdparam">x</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">y</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">width</var>, </td></tr><tr><td> </td><td>GLsizei <var class="pdparam">height</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">

<em class="parameter"><code>x</code></em>, <em class="parameter"><code>y</code></em>

</span></dt><dd><p>Specify the lower left corner of the scissor box, in pixels.

The initial value is (0, 0).</p></dd><dt><span class="term">

<em class="parameter"><code>width</code></em>, <em class="parameter"><code>height</code></em>

</span></dt><dd><p>Specify the width and height of the scissor box.

When a GL context is first attached to a surface (e.g. window),

<em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em>

are set to the dimensions of that surface.</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>

<code class="function">glScissor</code>

defines a rectangle, called the scissor box, in window

coordinates. The first two arguments,

<em class="parameter"><code>x</code></em> and

<em class="parameter"><code>y</code></em>, specify the lower left corner of the box.

<em class="parameter"><code>width</code></em> and <em class="parameter"><code>height</code></em>

specify the width and height of the box.</p><p>To enable and disable the scissor test, call

<a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> and

<a class="citerefentry" href="glDisable"><span class="citerefentry"><span class="refentrytitle">glDisable</span></span></a>

with argument <code class="constant">GL_SCISSOR_TEST</code>.

The scissor test is initially disabled. While scissor test is enabled,

only pixels that lie within the scissor box can be modified by

drawing commands. Window coordinates have integer values at the

shared corners of frame buffer pixels.

<code class="function">glScissor</code>(0, 0, 1, 1)

allows modification of only the lower left pixel in the window,

and <code class="function">glScissor</code>(0, 0, 0, 0)

doesn't allow modification of any pixels in the window.</p><p>When the scissor test is disabled, it is as though the

scissor box includes the entire window.</p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_VALUE</code> is generated if either

<em class="parameter"><code>width</code></em> or <em class="parameter"><code>height</code></em>

is negative.</p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p>

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

<a class="citerefentry" href="glViewport"><span class="citerefentry"><span class="refentrytitle">glViewport</span></span></a>

</p></div><div class="refsect1" title="Copyright"><a id="copyright"></a><h2>Copyright</h2><p>

Copyright © 2003-2004

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>