upstream-doc/man4/glDispatchComputeIndirect.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="glDispatchComputeIndirect">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2012</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glDispatchComputeIndirect</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glDispatchComputeIndirect</refname>
  17         <refpurpose>launch one or more compute work groups using parameters stored in a buffer</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glDispatchComputeIndirect</function></funcdef>
  23                 <paramdef>GLintptr <parameter>indirect</parameter></paramdef>
  24             </funcprototype>
  25         </funcsynopsis>
  26     </refsynopsisdiv>
  27     <refsect1 id="parameters"><title>Parameters</title>
  28         <variablelist>
  29         <varlistentry>
  30             <term><parameter>indirect</parameter></term>
  31             <listitem>
  32                 <para>
  33                     The offset into the buffer object currently bound to the
  34                     <constant>GL_DISPATCH_INDIRECT_BUFFER</constant> buffer target at
  35                     which the dispatch parameters are stored.
  36                 </para>
  37             </listitem>
  38         </varlistentry>
  39         </variablelist>
  40     </refsect1>
  41     <refsect1 id="description"><title>Description</title>
  42         <para>
  43             <function>glDispatchComputeIndirect</function> launches one or more compute
  44             work groups using parameters stored in the buffer object currently bound
  45             to the <constant>GL_DISPATCH_INDIRECT_BUFFER</constant> target.
  46             Each work group is processed by the active program object for the compute
  47             shader stage. While the individual shader invocations within a work group are
  48             executed as a unit, work groups are executed completely independently and in
  49             unspecified order. <parameter>indirect</parameter> contains the offset
  50             into the data store of the buffer object bound to the <constant>GL_DISPATCH_INDIRECT_BUFFER</constant>
  51             target at which the parameters are stored.
  52         </para>
  53         <para>
  54             The parameters addressed by <parameter>indirect</parameter> are packed a structure,
  55             which takes the form (in C):
  56             <programlisting><![CDATA[    typedef  struct {
  57         uint  num_groups_x;
  58         uint  num_groups_y;
  59         uint  num_groups_z;
  60     } DispatchIndirectCommand;]]></programlisting>
  61         </para>
  62         <para>
  63             A call to <function>glDispatchComputeIndirect</function> is equivalent, assuming no
  64             errors are generated, to:
  65             <programlisting><![CDATA[    cmd = (const DispatchIndirectCommand  *)indirect;
  66     glDispatchComputeIndirect(cmd->num_groups_x, cmd->num_groups_y, cmd->num_groups_z);
  67     }]]></programlisting>
  68         </para>
  69         <para>
  70             Unlike <citerefentry><refentrytitle>glDispatchCompute</refentrytitle></citerefentry>,
  71             no error is generated if any of the <code>num_groups_x</code>,
  72             <code>num_groups_y</code> or <code>num_groups_z</code> members
  73             of the <code>DispatchIndirectCommand</code> is larger than the
  74             value of <constant>GL_MAX_COMPUTE_WORK_GROUP_COUNT</constant> for the
  75             corresponding dimension. In such circumstances, behavior is undefined and
  76             may lead to application termination.
  77         </para>
  78     </refsect1>
  79     <refsect1 id="errors"><title>Errors</title>
  80         <para>
  81             <constant>GL_INVALID_OPERATION</constant> is generated if there is no active program
  82             for the compute shader stage.
  83         </para>
  84         <para>
  85             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>indirect</parameter> is
  86             less than zero or not a multiple of four.
  87         </para>
  88         <para>
  89             <constant>GL_INVALID_OPERATION</constant> is generated if no buffer is bound to the
  90             <constant>GL_DISPATCH_INDIRECT_BUFFER</constant> target or if the command would
  91             source data beyond the end of the buffer object's data store.
  92         </para>
  93     </refsect1>
  94     <refsect1 id="associatedgets"><title>Associated Gets</title>
  95         <para>
  96             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAX_COMPUTE_WORK_GROUP_COUNT</constant>
  97         </para>
  98     </refsect1>
  99     <refsect1 id="seealso"><title>See Also</title>
 100         <para>
 101             <citerefentry><refentrytitle>glDispatchCompute</refentrytitle></citerefentry>.
 102         </para>
 103     </refsect1>
 104     <refsect1 id="Copyright"><title>Copyright</title>
 105         <para>
 106             Copyright <trademark class="copyright"></trademark> 2012 Khronos Group.
 107             This material may be distributed subject to the terms and conditions set forth in
 108             the Open Publication License, v 1.0, 8 June 1999.
 109             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 110         </para>
 111     </refsect1>
 112 </refentry>