upstream-man-pages/man4/glLogicOp.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="glLogicOp">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glLogicOp</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glLogicOp</refname>
  17         <refpurpose>specify a logical pixel operation for rendering</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glLogicOp</function></funcdef>
  23                 <paramdef>GLenum <parameter>opcode</parameter></paramdef>
  24             </funcprototype>
  25         </funcsynopsis>
  26     </refsynopsisdiv>
  27     <refsect1 id="parameters"><title>Parameters</title>
  28         <variablelist>
  29         <varlistentry>
  30             <term><parameter>opcode</parameter></term>
  31             <listitem>
  32                 <para>
  33                     Specifies a symbolic constant that selects a logical operation.
  34                     The following symbols are accepted:
  35                     <constant>GL_CLEAR</constant>,
  36                     <constant>GL_SET</constant>,
  37                     <constant>GL_COPY</constant>,
  38                     <constant>GL_COPY_INVERTED</constant>,
  39                     <constant>GL_NOOP</constant>,
  40                     <constant>GL_INVERT</constant>,
  41                     <constant>GL_AND</constant>,
  42                     <constant>GL_NAND</constant>,
  43                     <constant>GL_OR</constant>,
  44                     <constant>GL_NOR</constant>,
  45                     <constant>GL_XOR</constant>,
  46                     <constant>GL_EQUIV</constant>,
  47                     <constant>GL_AND_REVERSE</constant>,
  48                     <constant>GL_AND_INVERTED</constant>,
  49                     <constant>GL_OR_REVERSE</constant>, and
  50                     <constant>GL_OR_INVERTED</constant>. The initial value is <constant>GL_COPY</constant>.
  51                 </para>
  52             </listitem>
  53         </varlistentry>
  54         </variablelist>
  55     </refsect1>
  56     <refsect1 id="description"><title>Description</title>
  57         <para>
  58             <function>glLogicOp</function> specifies a logical operation that,
  59             when enabled,
  60             is applied between the incoming RGBA color
  61             and the RGBA color at the corresponding location in the
  62             frame buffer.
  63             To enable or disable the logical operation, call
  64             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
  65             using the symbolic constant <constant>GL_COLOR_LOGIC_OP</constant>. The initial value is
  66             disabled.
  67         </para>
  68         <para>
  69         </para>
  70         <informaltable frame="topbot">
  71             <tgroup cols="2" align="left">
  72                 <colspec/>
  73                 <colspec/>
  74                 <thead>
  75                     <row>
  76                         <entry rowsep="1" align="left"><emphasis role="bold">
  77                         Opcode
  78                         </emphasis></entry>
  79                         <entry rowsep="1" align="left"><emphasis role="bold">
  80                         Resulting Operation
  81                         </emphasis></entry>
  82                     </row>
  83                 </thead>
  84                 <tbody>
  85                     <row>
  86                         <entry align="left">
  87                         <constant>GL_CLEAR</constant>
  88                         </entry>
  89                         <entry align="center">
  90                         0
  91                         </entry>
  92                     </row>
  93                     <row>
  94                         <entry align="left">
  95                         <constant>GL_SET</constant>
  96                         </entry>
  97                         <entry align="center">
  98                         1
  99                         </entry>
 100                     </row>
 101                     <row>
 102                         <entry align="left">
 103                         <constant>GL_COPY</constant>
 104                         </entry>
 105                         <entry align="center">
 106                         s
 107                         </entry>
 108                     </row>
 109                     <row>
 110                         <entry align="left">
 111                         <constant>GL_COPY_INVERTED</constant>
 112                         </entry>
 113                         <entry align="center">
 114                         ~s
 115                         </entry>
 116                     </row>
 117                     <row>
 118                         <entry align="left">
 119                         <constant>GL_NOOP</constant>
 120                         </entry>
 121                         <entry align="center">
 122                         d
 123                         </entry>
 124                     </row>
 125                     <row>
 126                         <entry align="left">
 127                         <constant>GL_INVERT</constant>
 128                         </entry>
 129                         <entry align="center">
 130                         ~d
 131                         </entry>
 132                     </row>
 133                     <row>
 134                         <entry align="left">
 135                         <constant>GL_AND</constant>
 136                         </entry>
 137                         <entry align="center">
 138                         s &amp; d
 139                         </entry>
 140                     </row>
 141                     <row>
 142                         <entry align="left">
 143                         <constant>GL_NAND</constant>
 144                         </entry>
 145                         <entry align="center">
 146                         ~(s &amp; d)
 147                         </entry>
 148                     </row>
 149                     <row>
 150                         <entry align="left">
 151                         <constant>GL_OR</constant>
 152                         </entry>
 153                         <entry align="center">
 154                         s | d
 155                         </entry>
 156                     </row>
 157                     <row>
 158                         <entry align="left">
 159                         <constant>GL_NOR</constant>
 160                         </entry>
 161                         <entry align="center">
 162                         ~(s | d)
 163                         </entry>
 164                     </row>
 165                     <row>
 166                         <entry align="left">
 167                         <constant>GL_XOR</constant>
 168                         </entry>
 169                         <entry align="center">
 170                         s ^ d
 171                         </entry>
 172                     </row>
 173                     <row>
 174                         <entry align="left">
 175                         <constant>GL_EQUIV</constant>
 176                         </entry>
 177                         <entry align="center">
 178                         ~(s ^ d)
 179                         </entry>
 180                     </row>
 181                     <row>
 182                         <entry align="left">
 183                         <constant>GL_AND_REVERSE</constant>
 184                         </entry>
 185                         <entry align="center">
 186                         s &amp; ~d
 187                         </entry>
 188                     </row>
 189                     <row>
 190                         <entry align="left">
 191                         <constant>GL_AND_INVERTED</constant>
 192                         </entry>
 193                         <entry align="center">
 194                         ~s &amp; d
 195                         </entry>
 196                     </row>
 197                     <row>
 198                         <entry align="left">
 199                         <constant>GL_OR_REVERSE</constant>
 200                         </entry>
 201                         <entry align="center">
 202                         s | ~d
 203                         </entry>
 204                     </row>
 205                     <row>
 206                         <entry align="left">
 207                         <constant>GL_OR_INVERTED</constant>
 208                         </entry>
 209                         <entry align="center">
 210                         ~s | d
 211                         </entry>
 212                     </row>
 213                 </tbody>
 214             </tgroup>
 215         </informaltable>
 216         <para>
 217             <parameter>opcode</parameter> is a symbolic constant chosen from the list above.
 218             In the explanation of the logical operations,
 219             <emphasis>s</emphasis> represents the incoming color and
 220             <emphasis>d</emphasis> represents the color in the frame buffer.
 221             Standard C-language operators are used.
 222             As these bitwise operators suggest,
 223             the logical operation is applied independently to each bit pair of the
 224             source and destination colors.
 225         </para>
 226     </refsect1>
 227     <refsect1 id="notes"><title>Notes</title>
 228         <para>
 229             When more than one RGBA color buffer is enabled for drawing,
 230             logical operations are performed separately for each enabled buffer,
 231             using for the destination value the contents of that buffer
 232             (see <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>).
 233         </para>
 234         <para>
 235             Logic operations have no effect on floating point draw buffers. However, if
 236             <constant>GL_COLOR_LOGIC_OP</constant> is enabled, blending is still disabled
 237             in this case.
 238         </para>
 239     </refsect1>
 240     <refsect1 id="errors"><title>Errors</title>
 241         <para>
 242             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>opcode</parameter> is not an accepted value.
 243         </para>
 244     </refsect1>
 245     <refsect1 id="associatedgets"><title>Associated Gets</title>
 246         <para>
 247             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LOGIC_OP_MODE</constant>.
 248         </para>
 249         <para>
 250             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_COLOR_LOGIC_OP</constant>.
 251         </para>
 252     </refsect1>
 253     <refsect1 id="seealso"><title>See Also</title>
 254         <para>
 255             <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>,
 256             <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
 257             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
 258             <citerefentry><refentrytitle>glStencilOp</refentrytitle></citerefentry>
 259         </para>
 260     </refsect1>
 261     <refsect1 id="Copyright"><title>Copyright</title>
 262         <para>
 263             Copyright <trademark class="copyright"></trademark> 1991-2006
 264             Silicon Graphics, Inc. This document is licensed under the SGI
 265             Free Software B License. For details, see
 266             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 267         </para>
 268     </refsect1>
 269 </refentry>