upstream-doc/man3/glSampleCoverage.xml

   1 <?xml version="1.0" encoding="UTF-8"?>
   2 <!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
   3               "http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
   4 <refentry id="glSampleCoverage">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glSampleCoverage</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glSampleCoverage</refname>
  17         <refpurpose>specify multisample coverage parameters</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glSampleCoverage</function></funcdef>
  23                 <paramdef>GLclampf <parameter>value</parameter></paramdef>
  24                 <paramdef>GLboolean <parameter>invert</parameter></paramdef>
  25             </funcprototype>
  26         </funcsynopsis>
  27     </refsynopsisdiv>
  28     <!-- eqn: ignoring delim $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>value</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specify a single floating-point sample coverage value.  The value is
  36                     clamped to the range
  37                     <inlineequation><mml:math>
  38                         <!-- eqn: [0 ,1]: -->
  39                         <mml:mfenced open="[" close="]">
  40                             <mml:mn>0</mml:mn>
  41                             <mml:mn>1</mml:mn>
  42                         </mml:mfenced>
  43                     </mml:math></inlineequation>.
  44                     The initial value is 1.0.
  45                 </para>
  46             </listitem>
  47         </varlistentry>
  48         <varlistentry>
  49             <term><parameter>invert</parameter></term>
  50             <listitem>
  51                 <para>
  52                     Specify a single boolean value representing if the coverage masks should be
  53                     inverted.  <constant>GL_TRUE</constant> and <constant>GL_FALSE</constant> are accepted.  The initial value
  54                     is <constant>GL_FALSE</constant>.
  55                 </para>
  56             </listitem>
  57         </varlistentry>
  58         </variablelist>
  59     </refsect1>
  60     <refsect1 id="description"><title>Description</title>
  61         <para>
  62             Multisampling samples a pixel multiple times at various
  63             implementation-dependent subpixel locations to generate antialiasing
  64             effects.  Multisampling transparently antialiases points, lines, polygons,
  65             and images if it is enabled.
  66         </para>
  67         <para>
  68             <parameter>value</parameter> is used in constructing a temporary mask used in determining which
  69             samples will be used in resolving the final fragment color.  This mask is
  70             bitwise-anded with the coverage mask generated from the multisampling
  71             computation.  If the <parameter>invert</parameter> flag is set, the temporary mask is inverted
  72             (all bits flipped) and then the bitwise-and is computed.
  73         </para>
  74         <para>
  75             If an implementation does not have any multisample buffers available, or
  76             multisampling is disabled, rasterization occurs with only a single sample
  77             computing a pixel's final RGB color.
  78         </para>
  79         <para>
  80             Provided an implementation supports multisample buffers, and multisampling
  81             is enabled, then a pixel's final color is generated by combining several
  82             samples per pixel.  Each sample contains color, depth, and stencil
  83             information, allowing those operations to be performed on each sample.
  84         </para>
  85     </refsect1>
  86     <refsect1 id="associatedgets"><title>Associated Gets</title>
  87         <para>
  88             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_VALUE</constant>
  89         </para>
  90         <para>
  91             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_INVERT</constant>
  92         </para>
  93         <para>
  94             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MULTISAMPLE</constant>
  95         </para>
  96         <para>
  97             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant>
  98         </para>
  99         <para>
 100             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_ONE</constant>
 101         </para>
 102         <para>
 103             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE</constant>
 104         </para>
 105     </refsect1>
 106     <refsect1 id="seealso"><title>See Also</title>
 107         <para>
 108             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>
 109         </para>
 110     </refsect1>
 111     <refsect1 id="Copyright"><title>Copyright</title>
 112         <para>
 113             Copyright <trademark class="copyright"></trademark> 1991-2006
 114             Silicon Graphics, Inc. This document is licensed under the SGI
 115             Free Software B License. For details, see
 116             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 117         </para>
 118     </refsect1>
 119 </refentry>