upstream-man-pages/man4/glDrawElementsInstancedBaseVertexBaseInstance.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="glDrawElementsInstancedBaseVertexBaseInstance">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glDrawElementsInstancedBaseVertexBaseInstance</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glDrawElementsInstancedBaseVertexBaseInstance</refname>
  17         <refpurpose>render multiple instances of a set of primitives from array data with a per-element offset</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glDrawElementsInstancedBaseVertexBaseInstance</function></funcdef>
  23                 <paramdef>GLenum <parameter>mode</parameter></paramdef>
  24                 <paramdef>GLsizei <parameter>count</parameter></paramdef>
  25                 <paramdef>GLenum <parameter>type</parameter></paramdef>
  26                 <paramdef>GLvoid *<parameter>indices</parameter></paramdef>
  27                 <paramdef>GLsizei <parameter>primcount</parameter></paramdef>
  28                 <paramdef>GLint <parameter>basevertex</parameter></paramdef>
  29                 <paramdef>GLuint <parameter>baseinstance</parameter></paramdef>
  30             </funcprototype>
  31         </funcsynopsis>
  32     </refsynopsisdiv>
  33     <!-- eqn: ignoring delim $$ -->
  34     <refsect1 id="parameters"><title>Parameters</title>
  35         <variablelist>
  36         <varlistentry>
  37             <term><parameter>mode</parameter></term>
  38             <listitem>
  39                 <para>
  40                     Specifies what kind of primitives to render.
  41                     Symbolic constants
  42                     <constant>GL_POINTS</constant>, <constant>GL_LINE_STRIP</constant>, <constant>GL_LINE_LOOP</constant>,
  43                     <constant>GL_LINES</constant>, <constant>GL_TRIANGLE_STRIP</constant>, <constant>GL_TRIANGLE_FAN</constant>,
  44                     <constant>GL_TRIANGLES</constant>, <constant>GL_LINES_ADJACENCY</constant>, <constant>GL_LINE_STRIP_ADJACENCY</constant>,
  45                     <constant>GL_TRIANGLES_ADJACENCY</constant>, <constant>GL_TRIANGLE_STRIP_ADJACENCY</constant> and <constant>GL_PATCHES</constant> are accepted.
  46                 </para>
  47             </listitem>
  48         </varlistentry>
  49         <varlistentry>
  50             <term><parameter>count</parameter></term>
  51             <listitem>
  52                 <para>
  53                     Specifies the number of elements to be rendered.
  54                 </para>
  55             </listitem>
  56         </varlistentry>
  57         <varlistentry>
  58             <term><parameter>type</parameter></term>
  59             <listitem>
  60                 <para>
  61                     Specifies the type of the values in indices. Must be one of <constant>GL_UNSIGNED_BYTE</constant>,
  62                     <constant>GL_UNSIGNED_SHORT</constant>, or <constant>GL_UNSIGNED_INT</constant>.
  63                 </para>
  64             </listitem>
  65         </varlistentry>
  66         <varlistentry>
  67             <term><parameter>indices</parameter></term>
  68             <listitem>
  69                 <para>
  70                     Specifies a pointer to the location where the indices are stored.
  71                 </para>
  72             </listitem>
  73         </varlistentry>
  74         <varlistentry>
  75             <term><parameter>primcount</parameter></term>
  76             <listitem>
  77                 <para>
  78                     Specifies the number of instances of the indexed geometry that should be drawn.
  79                 </para>
  80             </listitem>
  81         </varlistentry>
  82         <varlistentry>
  83             <term><parameter>basevertex</parameter></term>
  84             <listitem>
  85                 <para>
  86                     Specifies a constant that should be added to each element of <parameter>indices</parameter>
  87                     when chosing elements from the enabled vertex arrays.
  88                 </para>
  89             </listitem>
  90         </varlistentry>
  91         <varlistentry>
  92             <term><parameter>baseinstance</parameter></term>
  93             <listitem>
  94                 <para>
  95                     Specifies the base instance for use in fetching instanced vertex attributes.
  96                 </para>
  97             </listitem>
  98         </varlistentry>
  99         </variablelist>
 100     </refsect1>
 101     <refsect1 id="description"><title>Description</title>
 102         <para>
 103             <function>glDrawElementsInstancedBaseVertexBaseInstance</function> behaves identically to
 104             <citerefentry><refentrytitle>glDrawElementsInstanced</refentrytitle></citerefentry> except that the <emphasis>i</emphasis>th element
 105             transferred by the corresponding draw call will be taken from element <parameter>indices</parameter>[i] + <parameter>basevertex</parameter>
 106             of each enabled array. If the resulting value is larger than the maximum value representable by <parameter>type</parameter>,
 107             it is as if the calculation were upconverted to 32-bit unsigned integers (with wrapping on overflow conditions).
 108             The operation is undefined if the sum would be negative. The <parameter>basevertex</parameter> has no effect on the
 109             shader-visible value of <constant>gl_VertexID</constant>.
 110         </para>
 111         <para>
 112             Specific vertex attributes may be classified as <emphasis>instanced</emphasis> through the use of
 113             <citerefentry><refentrytitle>glVertexAttribDivisor</refentrytitle></citerefentry>. Instanced vertex attributes
 114             supply per-instance vertex data to the vertex shader. The index of the vertex fetched from the enabled instanced vertex
 115             attribute arrays is calculated as
 116 <mml:math>
 117   <mml:mrow>
 118     <mml:mfenced open = '&lfloor;' close = '&rfloor;'>
 119       <mml:mfrac>
 120         <mml:mrow>
 121           <mml:mi>gl</mml:mi>
 122           <mml:mo>_</mml:mo>
 123           <mml:mi>InstanceID</mml:mi>
 124         </mml:mrow>
 125         <mml:mi>divisor</mml:mi>
 126       </mml:mfrac>
 127     </mml:mfenced>
 128     <mml:mo lspace='2px' rspace='2px'>&plus;</mml:mo>
 129     <mml:mi>baseInstance</mml:mi>
 130   </mml:mrow>
 131 </mml:math>. Note that <parameter>baseinstance</parameter> does not affect the shader-visible value of <constant>gl_InstanceID</constant>.
 132         </para>
 133     </refsect1>
 134     <refsect1 id="notes"><title>Notes</title>
 135         <function>glDrawElementsInstancedBaseVertex</function> is only supported if the GL version is 3.2 or greater.
 136     </refsect1>
 137     <refsect1 id="errors"><title>Errors</title>
 138         <para>
 139             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not an accepted value.
 140         </para>
 141         <para>
 142             <constant>GL_INVALID_VALUE</constant> is generated if <parameter>count</parameter> or <parameter>primcount</parameter> is negative.
 143         </para>
 144         <para>
 145             <constant>GL_INVALID_OPERATION</constant> is generated if a geometry shader is active and <parameter>mode</parameter>
 146             is incompatible with the input primitive type of the geometry shader in the currently installed program object.
 147         </para>
 148         <para>
 149             <constant>GL_INVALID_OPERATION</constant> is generated if a non-zero buffer object name is bound to an
 150             enabled array or the element array and the buffer object's data store is currently mapped.
 151         </para>
 152     </refsect1>
 153     <refsect1 id="seealso"><title>See Also</title>
 154         <para>
 155             <citerefentry><refentrytitle>glDrawElements</refentrytitle></citerefentry>,
 156             <citerefentry><refentrytitle>glDrawRangeElements</refentrytitle></citerefentry>,
 157             <citerefentry><refentrytitle>glDrawRangeElementsBaseVertex</refentrytitle></citerefentry>,
 158             <citerefentry><refentrytitle>glDrawElementsInstanced</refentrytitle></citerefentry>,
 159             <citerefentry><refentrytitle>glDrawElementsInstancedBaseVertex</refentrytitle></citerefentry>
 160         </para>
 161     </refsect1>
 162     <refsect1 id="Copyright"><title>Copyright</title>
 163         <para>
 164             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
 165             This material may be distributed subject to the terms and conditions set forth in
 166             the Open Publication License, v 1.0, 8 June 1999.
 167             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 168         </para>
 169     </refsect1>
 170 </refentry>