128 lines
5.4 KiB
XML
128 lines
5.4 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="glDepthRange">
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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>glDepthRange</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glDepthRange</refname>
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<refpurpose>specify mapping of depth values from normalized device coordinates to window coordinates</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>glDepthRange</function></funcdef>
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<paramdef>GLclampd <parameter>nearVal</parameter></paramdef>
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<paramdef>GLclampd <parameter>farVal</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<!-- eqn: ignoring delim $$ -->
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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>nearVal</parameter></term>
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<listitem>
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<para>
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Specifies the mapping of the near clipping plane to window coordinates.
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The initial value is 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>farVal</parameter></term>
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<listitem>
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<para>
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Specifies the mapping of the far clipping plane to window coordinates.
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The initial value is 1.
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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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After clipping and division by <emphasis>w</emphasis>,
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depth coordinates range from
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<inlineequation><mml:math>
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<!-- eqn: -1:-->
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<mml:mn>-1</mml:mn>
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</mml:math></inlineequation>
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to 1,
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corresponding to the near and far clipping planes.
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<function>glDepthRange</function> specifies a linear mapping of the normalized depth coordinates
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in this range to window depth coordinates.
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Regardless of the actual depth buffer implementation,
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window coordinate depth values are treated as though they range
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from 0 through 1 (like color components).
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Thus,
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the values accepted by <function>glDepthRange</function> are both clamped to this range
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before they are accepted.
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</para>
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<para>
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The setting of (0,1) maps the near plane to 0 and
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the far plane to 1.
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With this mapping,
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the depth buffer range is fully utilized.
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</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para>
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It is not necessary that <parameter>nearVal</parameter> be less than <parameter>farVal</parameter>.
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Reverse mappings such as
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<inlineequation><mml:math>
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<!-- eqn: nearVal = 1:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">nearVal</mml:mi>
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<mml:mo>=</mml:mo>
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<mml:mn>1</mml:mn>
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</mml:mrow>
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</mml:math></inlineequation>,
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and
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<inlineequation><mml:math>
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<!-- eqn: farVal = 0:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">farVal</mml:mi>
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<mml:mo>=</mml:mo>
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<mml:mn>0</mml:mn>
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</mml:mrow>
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</mml:math></inlineequation>
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are acceptable.
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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_OPERATION</constant> is generated if <function>glDepthRange</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_DEPTH_RANGE</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>glDepthFunc</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glPolygonOffset</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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