114 lines
5.2 KiB
XML
114 lines
5.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glScissor">
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<refmeta>
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<refmetainfo>
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<copyright>
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<year>1991-2006</year>
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<holder>Silicon Graphics, Inc.</holder>
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</copyright>
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</refmetainfo>
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<refentrytitle>glScissor</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glScissor</refname>
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<refpurpose>define the scissor box</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glScissor</function></funcdef>
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<paramdef>GLint <parameter>x</parameter></paramdef>
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<paramdef>GLint <parameter>y</parameter></paramdef>
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<paramdef>GLsizei <parameter>width</parameter></paramdef>
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<paramdef>GLsizei <parameter>height</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>x</parameter></term>
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<term><parameter>y</parameter></term>
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<listitem>
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<para>
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Specify the lower left corner of the scissor box.
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Initially (0, 0).
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>width</parameter></term>
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<term><parameter>height</parameter></term>
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<listitem>
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<para>
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Specify the width and height of the scissor box.
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When a GL context is first attached to a window,
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<parameter>width</parameter> and <parameter>height</parameter> are set to the dimensions of that
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window.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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<function>glScissor</function> defines a rectangle, called the scissor box,
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in window coordinates.
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The first two arguments,
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<parameter>x</parameter> and <parameter>y</parameter>,
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specify the lower left corner of the box.
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<parameter>width</parameter> and <parameter>height</parameter> specify the width and height of the box.
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</para>
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<para>
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To enable and disable the scissor test, call
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<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument
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<constant>GL_SCISSOR_TEST</constant>. The test is initially disabled.
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While the test is enabled, only pixels that lie within the scissor box
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can be modified by drawing commands.
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Window coordinates have integer values at the shared corners of
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frame buffer pixels.
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<code>glScissor(0,0,1,1)</code> allows modification of only the lower left
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pixel in the window, and <code>glScissor(0,0,0,0)</code> doesn't allow
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modification of any pixels in the window.
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</para>
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<para>
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When the scissor test is disabled,
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it is as though the scissor box includes the entire window.
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</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para>
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<constant>GL_INVALID_VALUE</constant> is generated if either <parameter>width</parameter> or <parameter>height</parameter> is negative.
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</para>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if <function>glScissor</function>
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is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
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and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
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</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SCISSOR_BOX</constant>
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</para>
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<para>
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<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SCISSOR_TEST</constant>
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</para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glViewport</refentrytitle></citerefentry>
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</para>
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</refsect1>
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<refsect1 id="Copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"></trademark> 1991-2006
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Silicon Graphics, Inc. This document is licensed under the SGI
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Free Software B License. For details, see
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<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
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</para>
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</refsect1>
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</refentry>
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