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<!DOCTYPE refentry [ <!ENTITY % mathent SYSTEM "math.ent"> %mathent; ]>
<!-- Converted by db4-upgrade version 1.1 -->
<refentry xmlns="http://docbook.org/ns/docbook" version="5.0" xml:id="glHint">
<info>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
<copyright>
<year>2010-2014</year>
<holder>Khronos Group</holder>
</copyright>
</info>
<refmeta>
<refentrytitle>glHint</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glHint</refname>
<refpurpose>specify implementation-specific hints</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glHint</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLenum <parameter>mode</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 xml:id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
Specifies a symbolic constant indicating the behavior to be controlled.
<constant>GL_LINE_SMOOTH_HINT</constant>,
<constant>GL_POLYGON_SMOOTH_HINT</constant>,
<constant>GL_TEXTURE_COMPRESSION_HINT</constant>, and
<constant>GL_FRAGMENT_SHADER_DERIVATIVE_HINT</constant>
are accepted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>mode</parameter></term>
<listitem>
<para>
Specifies a symbolic constant indicating the desired behavior.
<constant>GL_FASTEST</constant>,
<constant>GL_NICEST</constant>, and
<constant>GL_DONT_CARE</constant> are accepted.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 xml:id="description"><title>Description</title>
<para>
Certain aspects of GL behavior,
when there is room for interpretation,
can be controlled with hints.
A hint is specified with two arguments.
<parameter>target</parameter> is a symbolic
constant indicating the behavior to be controlled,
and <parameter>mode</parameter> is another symbolic constant indicating the desired
behavior. The initial value for each <parameter>target</parameter> is <constant>GL_DONT_CARE</constant>.
<parameter>mode</parameter> can be one of the following:
</para>
<variablelist>
<varlistentry>
<term><constant>GL_FASTEST</constant></term>
<listitem>
<para>
</para>
<para>
The most efficient option should be chosen.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_NICEST</constant></term>
<listitem>
<para>
</para>
<para>
The most correct,
or highest quality,
option should be chosen.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_DONT_CARE</constant></term>
<listitem>
<para>
</para>
<para>
No preference.
</para>
</listitem>
</varlistentry>
</variablelist>
<para>
Though the implementation aspects that can be hinted are well defined,
the interpretation of the hints depends on the implementation.
The hint aspects that can be specified with <parameter>target</parameter>,
along with suggested semantics,
are as follows:
</para>
<variablelist>
<varlistentry>
<term><constant>GL_FRAGMENT_SHADER_DERIVATIVE_HINT</constant></term>
<listitem>
<para>
</para>
<para>
Indicates the accuracy of the derivative calculation for the GL shading language fragment processing built-in functions:
<constant>dFdx</constant>, <constant>dFdy</constant>, and <constant>fwidth</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_LINE_SMOOTH_HINT</constant></term>
<listitem>
<para>
</para>
<para>
Indicates the sampling quality of antialiased lines.
If a larger filter function is applied, hinting <constant>GL_NICEST</constant> can
result in more pixel fragments being generated during rasterization.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_POLYGON_SMOOTH_HINT</constant></term>
<listitem>
<para>
</para>
<para>
Indicates the sampling quality of antialiased polygons.
Hinting <constant>GL_NICEST</constant> can result in more pixel fragments being generated
during rasterization,
if a larger filter function is applied.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_COMPRESSION_HINT</constant></term>
<listitem>
<para>
</para>
<para>
Indicates the quality and performance of the compressing texture images.
Hinting <constant>GL_FASTEST</constant> indicates that texture images should be compressed
as quickly as possible, while <constant>GL_NICEST</constant> indicates that texture images
should be compressed with as little image quality loss as possible.
<constant>GL_NICEST</constant> should be selected if the texture is to be retrieved by
<citerefentry><refentrytitle>glGetCompressedTexImage</refentrytitle></citerefentry> for reuse.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 xml:id="notes"><title>Notes</title>
<para>
The interpretation of hints depends on the implementation.
Some implementations ignore <function>glHint</function> settings.
</para>
</refsect1>
<refsect1 xml:id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if either <parameter>target</parameter> or <parameter>mode</parameter> is not
an accepted value.
</para>
</refsect1>
<refsect1 xml:id="versions"><title>Version Support</title>
<informaltable>
<tgroup cols="13" align="left">
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apifunchead.xml" xpointer="xpointer(/*/*)"/>
<tbody>
<row>
<entry><function>glHint</function></entry>
<xi:include xmlns:xi="http://www.w3.org/2001/XInclude" href="apiversion.xml" xpointer="xpointer(/*/*[@role='20']/*)"/>
</row>
</tbody>
</tgroup>
</informaltable>
</refsect1>
<refsect1 xml:id="seealso"><title>See Also</title>
<!-- TBD -->
</refsect1>
<refsect1 xml:id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"/> 1991-2006 Silicon Graphics, Inc.
Copyright <trademark class="copyright"/> 2010-2014 Khronos Group.
This document is licensed under the SGI Free Software B License.
For details, see
<link xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</link>.
</para>
</refsect1>
</refentry>
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