upstream-man-pages/manglsl/textureGatherOffset.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="textureGatherOffset">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>2011</year>
   9                 <holder>Khronos Group</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>textureGatherOffset</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>textureGatherOffset</refname>
  17         <refpurpose>gathers four texels from a texture with offset</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>Declaration</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>gvec4 <function>textureGatherOffset</function></funcdef>
  23                 <paramdef>gsampler2D <parameter>sampler</parameter></paramdef>
  24                 <paramdef>vec2 <parameter>P</parameter></paramdef>
  25                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  26                 <paramdef>[int <parameter>comp]</parameter></paramdef>
  27             </funcprototype>
  28             <funcprototype>
  29                 <funcdef>gvec4 <function>textureGatherOffset</function></funcdef>
  30                 <paramdef>gsampler2DArray <parameter>sampler</parameter></paramdef>
  31                 <paramdef>vec3 <parameter>P</parameter></paramdef>
  32                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  33                 <paramdef>[int <parameter>comp]</parameter></paramdef>
  34             </funcprototype>
  35             <funcprototype>
  36                 <funcdef>gvec4 <function>textureGatherOffset</function></funcdef>
  37                 <paramdef>gsampler2DRect <parameter>sampler</parameter></paramdef>
  38                 <paramdef>vec3 <parameter>P</parameter></paramdef>
  39                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  40                 <paramdef>[int <parameter>comp]</parameter></paramdef>
  41             </funcprototype>
  42             <funcprototype>
  43                 <funcdef>vec4 <function>textureGatherOffset</function></funcdef>
  44                 <paramdef>gsampler2DShadow <parameter>sampler</parameter></paramdef>
  45                 <paramdef>vec2 <parameter>P</parameter></paramdef>
  46                 <paramdef>float <parameter>refZ</parameter></paramdef>
  47                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  48             </funcprototype>
  49             <funcprototype>
  50                 <funcdef>vec4 <function>textureGatherOffset</function></funcdef>
  51                 <paramdef>gsampler2DArrayShadow <parameter>sampler</parameter></paramdef>
  52                 <paramdef>vec3 <parameter>P</parameter></paramdef>
  53                 <paramdef>float <parameter>refZ</parameter></paramdef>
  54                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  55             </funcprototype>
  56             <funcprototype>
  57                 <funcdef>vec4 <function>textureGatherOffset</function></funcdef>
  58                 <paramdef>gsampler2DRectShadow <parameter>sampler</parameter></paramdef>
  59                 <paramdef>vec3 <parameter>P</parameter></paramdef>
  60                 <paramdef>float <parameter>refZ</parameter></paramdef>
  61                 <paramdef>ivec2 <parameter>offset</parameter></paramdef>
  62             </funcprototype>
  63         </funcsynopsis>
  64     </refsynopsisdiv>
  65     <refsect1 id="parameters"><title>Parameters</title>
  66         <variablelist>
  67         <varlistentry>
  68             <term><parameter>sampler</parameter></term>
  69             <listitem>
  70                 <para>
  71                     Specifies the sampler to which the texture from which texels will be retrieved is bound.
  72                 </para>
  73             </listitem>
  74         </varlistentry>
  75         <varlistentry>
  76             <term><parameter>P</parameter></term>
  77             <listitem>
  78                 <para>
  79                     Specifies the texture coordinates at which texture will be sampled.
  80                 </para>
  81             </listitem>
  82         </varlistentry>
  83         <varlistentry>
  84             <term><parameter>comp</parameter></term>
  85             <listitem>
  86                 <para>
  87                     Specifies the component of the source texture that will be used to generate the resulting vector.
  88                 </para>
  89             </listitem>
  90         </varlistentry>
  91         <varlistentry>
  92             <term><parameter>refZ</parameter></term>
  93             <listitem>
  94                 <para>
  95                     Specifies the reference Z value used in the comparison for shadow forms.
  96                 </para>
  97             </listitem>
  98         </varlistentry>
  99         <varlistentry>
 100             <term><parameter>offset</parameter></term>
 101             <listitem>
 102                 <para>
 103                     Specifies the offset from the specified texture coordinate <parameter>P</parameter> from which the texels will be gathered.
 104                 </para>
 105             </listitem>
 106         </varlistentry>
 107         </variablelist>
 108     </refsect1>
 109     <refsect1 id="description"><title>Description</title>
 110         <para>
 111             <function>textureGatherOffset</function> returns the value:
 112         </para>
 113         <para>
 114 <programlisting><![CDATA[    vec4(Sample_i0_j1(P + offset, base).comp,
 115          Sample_i1_j1(P + offset, base).comp,
 116          Sample_i1_j0(P + offset, base).comp,
 117          Sample_i0_j9(P + offset, base).comp);]]></programlisting>
 118     </para>
 119     <para>
 120         It perfoms as <citerefentry><refentrytitle>textureGather</refentrytitle></citerefentry> but with <parameter>offset</parameter>
 121         applied as described in <citerefentry><refentrytitle>textureOffset</refentrytitle></citerefentry>, except that the
 122         implementation-dependent minimum and maximum offset values are given by <constant>GL_MIN_PROGRRAM_TEXTURE_GATHER_OFFSET</constant>
 123         and <constant>GL_MAX_PROGRAM_TEXTURE_GATHER_OFFSET</constant>, respectively.
 124     </para>
 125     <para>
 126         If specified, the value of <parameter>comp</parameter> must ba constant integer expression with a value
 127         of 0, 1, 2, or 3, identifying the x, y, z or w component of the four-component vector lookup result for each
 128         texel, respectively. If <parameter>comp</parameter> is not specified, it is treated as 0, selecting the x
 129         component of each texel to generate the result.
 130     </para>
 131     </refsect1>
 132     <refsect1 id="versions"><title>Version Support</title>
 133         <informaltable frame="topbot">
 134             #VARTABLECOLS#
 135                 <thead>
 136                     #FUNCTABLEHEADER#
 137                     <row>
 138                         <entry>textureGatherOffset</entry>#newin40#
 139                     </row>
 140                 </thead>
 141             </tgroup>
 142         </informaltable>
 143     </refsect1>
 144     <refsect1 id="seealso"><title>See Also</title>
 145         <para>
 146             <citerefentry><refentrytitle>texelFetch</refentrytitle></citerefentry>,
 147             <citerefentry><refentrytitle>texelFetchOffset</refentrytitle></citerefentry>,
 148             <citerefentry><refentrytitle>texture</refentrytitle></citerefentry>,
 149             <citerefentry><refentrytitle>textureGather</refentrytitle></citerefentry>,
 150             <citerefentry><refentrytitle>textureGatherOffsets</refentrytitle></citerefentry>,
 151             <citerefentry><refentrytitle>textureGrad</refentrytitle></citerefentry>,
 152             <citerefentry><refentrytitle>textureGradOffset</refentrytitle></citerefentry>,
 153             <citerefentry><refentrytitle>textureLod</refentrytitle></citerefentry>,
 154             <citerefentry><refentrytitle>textureLodOffset</refentrytitle></citerefentry>,
 155             <citerefentry><refentrytitle>textureOffset</refentrytitle></citerefentry>,
 156             <citerefentry><refentrytitle>textureProj</refentrytitle></citerefentry>,
 157             <citerefentry><refentrytitle>textureProjGrad</refentrytitle></citerefentry>,
 158             <citerefentry><refentrytitle>textureProjGradOffset</refentrytitle></citerefentry>,
 159             <citerefentry><refentrytitle>textureProjLod</refentrytitle></citerefentry>,
 160             <citerefentry><refentrytitle>textureProjLodOffset</refentrytitle></citerefentry>,
 161             <citerefentry><refentrytitle>textureProjOffset</refentrytitle></citerefentry>,
 162             <citerefentry><refentrytitle>textureQueryLod</refentrytitle></citerefentry>,
 163             <citerefentry><refentrytitle>textureSize</refentrytitle></citerefentry>
 164         </para>
 165     </refsect1>
 166     <refsect1 id="Copyright"><title>Copyright</title>
 167         <para>
 168             Copyright <trademark class="copyright"></trademark> 2011 Khronos Group.
 169             This material may be distributed subject to the terms and conditions set forth in
 170             the Open Publication License, v 1.0, 8 June 1999.
 171             <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
 172         </para>
 173     </refsect1>
 174 </refentry>