upstream-doc/man4/glBlendEquation.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="glBlendEquation">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glBlendEquation</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glBlendEquation</refname>
  17         <refpurpose>specify the equation used for both the RGB blend equation and the Alpha blend equation</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glBlendEquation</function></funcdef>
  23                 <paramdef>GLenum <parameter>mode</parameter></paramdef>
  24             </funcprototype>
  25             <funcprototype>
  26                 <funcdef>void <function>glBlendEquationi</function></funcdef>
  27                 <paramdef>GLuint <parameter>buf</parameter></paramdef>
  28                 <paramdef>GLenum <parameter>mode</parameter></paramdef>
  29             </funcprototype>
  30         </funcsynopsis>
  31     </refsynopsisdiv>
  32     <!-- eqn: ignoring delim $$ -->
  33     <refsect1 id="parameters"><title>Parameters</title>
  34         <variablelist>
  35         <varlistentry>
  36             <term><parameter>buf</parameter></term>
  37             <listitem>
  38                 <para>
  39                     for <function>glBlendEquationi</function>, specifies the index of the draw buffer
  40                     for which to set the blend equation.
  41                 </para>
  42             </listitem>
  43         </varlistentry>
  44         <varlistentry>
  45             <term><parameter>mode</parameter></term>
  46             <listitem>
  47                 <para>
  48                     specifies how source and destination colors are combined.
  49                     It must be <constant>GL_FUNC_ADD</constant>, <constant>GL_FUNC_SUBTRACT</constant>,
  50                     <constant>GL_FUNC_REVERSE_SUBTRACT</constant>, <constant>GL_MIN</constant>, <constant>GL_MAX</constant>.
  51                 </para>
  52             </listitem>
  53         </varlistentry>
  54         </variablelist>
  55     </refsect1>
  56     <refsect1 id="description"><title>Description</title>
  57         <para>
  58             The blend equations determine how a new pixel (the ''source'' color)
  59             is combined with a pixel already in the framebuffer (the ''destination''
  60             color).  This function sets both the RGB blend equation and the alpha
  61             blend equation to a single equation. <function>glBlendEquationi</function>
  62             specifies the blend equation for a single draw buffer whereas <function>glBlendEquation</function>
  63             sets the blend equation for all draw buffers.
  64         </para>
  65         <para>
  66             These equations use the source and destination blend factors
  67             specified by either <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry> or
  68             <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>.
  69             See <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>
  70             for a description of the various blend factors.
  71         </para>
  72         <para>
  73             In the equations that follow, source and destination
  74             color components are referred to as
  75             <inlineequation><mml:math>
  76                 <!-- eqn: ( R sub s, G sub s, B sub s, A sub s ): -->
  77                 <mml:mfenced open="(" close=")">
  78                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
  79                     <mml:mi mathvariant="italic">s</mml:mi>
  80                     </mml:msub>
  81                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
  82                     <mml:mi mathvariant="italic">s</mml:mi>
  83                     </mml:msub>
  84                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
  85                     <mml:mi mathvariant="italic">s</mml:mi>
  86                     </mml:msub>
  87                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
  88                     <mml:mi mathvariant="italic">s</mml:mi>
  89                     </mml:msub>
  90                 </mml:mfenced>
  91             </mml:math></inlineequation>
  92             and
  93             <inlineequation><mml:math>
  94                 <!-- eqn: ( R sub d, G sub d, B sub d, A sub d ): -->
  95                 <mml:mfenced open="(" close=")">
  96                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
  97                     <mml:mi mathvariant="italic">d</mml:mi>
  98                     </mml:msub>
  99                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 100                     <mml:mi mathvariant="italic">d</mml:mi>
 101                     </mml:msub>
 102                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 103                     <mml:mi mathvariant="italic">d</mml:mi>
 104                     </mml:msub>
 105                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 106                     <mml:mi mathvariant="italic">d</mml:mi>
 107                     </mml:msub>
 108                 </mml:mfenced>
 109             </mml:math></inlineequation>,
 110             respectively.
 111             The result color is referred to as
 112             <inlineequation><mml:math>
 113                 <!-- eqn: ( R sub r, G sub r, B sub r, A sub r ): -->
 114                 <mml:mfenced open="(" close=")">
 115                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 116                     <mml:mi mathvariant="italic">r</mml:mi>
 117                     </mml:msub>
 118                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 119                     <mml:mi mathvariant="italic">r</mml:mi>
 120                     </mml:msub>
 121                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 122                     <mml:mi mathvariant="italic">r</mml:mi>
 123                     </mml:msub>
 124                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 125                     <mml:mi mathvariant="italic">r</mml:mi>
 126                     </mml:msub>
 127                 </mml:mfenced>
 128             </mml:math></inlineequation>.
 129             The source and destination blend factors are denoted
 130             <inlineequation><mml:math>
 131                 <!-- eqn: ( s sub R, s sub G, s sub B, s sub A ): -->
 132                 <mml:mfenced open="(" close=")">
 133                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 134                     <mml:mi mathvariant="italic">R</mml:mi>
 135                     </mml:msub>
 136                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 137                     <mml:mi mathvariant="italic">G</mml:mi>
 138                     </mml:msub>
 139                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 140                     <mml:mi mathvariant="italic">B</mml:mi>
 141                     </mml:msub>
 142                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 143                     <mml:mi mathvariant="italic">A</mml:mi>
 144                     </mml:msub>
 145                 </mml:mfenced>
 146             </mml:math></inlineequation>
 147             and
 148             <inlineequation><mml:math>
 149                 <!-- eqn: ( d sub R, d sub G, d sub B, d sub A ): -->
 150                 <mml:mfenced open="(" close=")">
 151                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 152                     <mml:mi mathvariant="italic">R</mml:mi>
 153                     </mml:msub>
 154                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 155                     <mml:mi mathvariant="italic">G</mml:mi>
 156                     </mml:msub>
 157                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 158                     <mml:mi mathvariant="italic">B</mml:mi>
 159                     </mml:msub>
 160                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 161                     <mml:mi mathvariant="italic">A</mml:mi>
 162                     </mml:msub>
 163                 </mml:mfenced>
 164             </mml:math></inlineequation>,
 165             respectively.
 166             For these equations all color components are understood to have values
 167             in the range
 168             <inlineequation><mml:math>
 169                 <!-- eqn: [0,1]: -->
 170                 <mml:mfenced open="[" close="]">
 171                     <mml:mn>0</mml:mn>
 172                     <mml:mn>1</mml:mn>
 173                 </mml:mfenced>
 174             </mml:math></inlineequation>.
 175
 176         <informaltable frame="topbot">
 177             <tgroup cols="3" align="left">
 178                 <colspec colwidth="1.1*" />
 179                 <colspec colwidth="1*" />
 180                 <colspec colwidth="1*" />
 181                 <thead>
 182                     <row>
 183                         <entry rowsep="1" align="left"><emphasis role="bold">
 184                         Mode
 185                         </emphasis></entry>
 186                         <entry rowsep="1" align="left"><emphasis role="bold">
 187                         RGB Components
 188                         </emphasis></entry>
 189                         <entry rowsep="1" align="left"><emphasis role="bold">
 190                         Alpha Component
 191                         </emphasis></entry>
 192                     </row>
 193                 </thead>
 194                 <tbody>
 195                     <row>
 196                         <entry align="left">
 197                         <constant>GL_FUNC_ADD</constant>
 198                         </entry>
 199                         <entry align="left">
 200                         <informalequation><mml:math>
 201                             <!-- eqn: Rr  =      R sub s s sub R  +  R sub d d sub R : -->
 202                             <mml:mrow>
 203                                 <mml:mi mathvariant="italic">Rr</mml:mi>
 204                                 <mml:mo>=</mml:mo>
 205                                 <mml:mrow>
 206                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 207                                     <mml:mi mathvariant="italic">s</mml:mi>
 208                                     </mml:msub>
 209                                     <mml:mo>&it;</mml:mo>
 210                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 211                                     <mml:mi mathvariant="italic">R</mml:mi>
 212                                     </mml:msub>
 213                                     <mml:mo>+</mml:mo>
 214                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 215                                     <mml:mi mathvariant="italic">d</mml:mi>
 216                                     </mml:msub>
 217                                     <mml:mo>&it;</mml:mo>
 218                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 219                                     <mml:mi mathvariant="italic">R</mml:mi>
 220                                     </mml:msub>
 221                                 </mml:mrow>
 222                             </mml:mrow>
 223                         </mml:math></informalequation>
 224                         <informalequation><mml:math>
 225                             <!-- eqn: Gr  =    G sub s s sub G  +  G sub d d sub G : -->
 226                             <mml:mrow>
 227                                 <mml:mi mathvariant="italic">Gr</mml:mi>
 228                                 <mml:mo>=</mml:mo>
 229                                 <mml:mrow>
 230                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 231                                     <mml:mi mathvariant="italic">s</mml:mi>
 232                                     </mml:msub>
 233                                     <mml:mo>&it;</mml:mo>
 234                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 235                                     <mml:mi mathvariant="italic">G</mml:mi>
 236                                     </mml:msub>
 237                                     <mml:mo>+</mml:mo>
 238                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 239                                     <mml:mi mathvariant="italic">d</mml:mi>
 240                                     </mml:msub>
 241                                     <mml:mo>&it;</mml:mo>
 242                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 243                                     <mml:mi mathvariant="italic">G</mml:mi>
 244                                     </mml:msub>
 245                                 </mml:mrow>
 246                             </mml:mrow>
 247                         </mml:math></informalequation>
 248                         <informalequation><mml:math>
 249                             <!-- eqn: Br  =    B sub s s sub B  +  B sub d d sub B : -->
 250                             <mml:mrow>
 251                                 <mml:mi mathvariant="italic">Br</mml:mi>
 252                                 <mml:mo>=</mml:mo>
 253                                 <mml:mrow>
 254                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 255                                     <mml:mi mathvariant="italic">s</mml:mi>
 256                                     </mml:msub>
 257                                     <mml:mo>&it;</mml:mo>
 258                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 259                                     <mml:mi mathvariant="italic">B</mml:mi>
 260                                     </mml:msub>
 261                                     <mml:mo>+</mml:mo>
 262                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 263                                     <mml:mi mathvariant="italic">d</mml:mi>
 264                                     </mml:msub>
 265                                     <mml:mo>&it;</mml:mo>
 266                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 267                                     <mml:mi mathvariant="italic">B</mml:mi>
 268                                     </mml:msub>
 269                                 </mml:mrow>
 270                             </mml:mrow>
 271                         </mml:math></informalequation>
 272                         </entry>
 273                         <entry align="left">
 274                         <informalequation><mml:math>
 275                             <!-- eqn: Ar  =    A sub s s sub A  +  A sub d d sub A : -->
 276                             <mml:mrow>
 277                                 <mml:mi mathvariant="italic">Ar</mml:mi>
 278                                 <mml:mo>=</mml:mo>
 279                                 <mml:mrow>
 280                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 281                                     <mml:mi mathvariant="italic">s</mml:mi>
 282                                     </mml:msub>
 283                                     <mml:mo>&it;</mml:mo>
 284                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 285                                     <mml:mi mathvariant="italic">A</mml:mi>
 286                                     </mml:msub>
 287                                     <mml:mo>+</mml:mo>
 288                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 289                                     <mml:mi mathvariant="italic">d</mml:mi>
 290                                     </mml:msub>
 291                                     <mml:mo>&it;</mml:mo>
 292                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 293                                     <mml:mi mathvariant="italic">A</mml:mi>
 294                                     </mml:msub>
 295                                 </mml:mrow>
 296                             </mml:mrow>
 297                         </mml:math></informalequation>
 298                         </entry>
 299                     </row>
 300                     <row>
 301                         <entry align="left">
 302                         <constant>GL_FUNC_SUBTRACT</constant>
 303                         </entry>
 304                         <entry align="left">
 305                         <informalequation><mml:math>
 306                             <!-- eqn: Rr  =      R sub s s sub R  -  R sub d d sub R : -->
 307                             <mml:mrow>
 308                                 <mml:mi mathvariant="italic">Rr</mml:mi>
 309                                 <mml:mo>=</mml:mo>
 310                                 <mml:mrow>
 311                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 312                                     <mml:mi mathvariant="italic">s</mml:mi>
 313                                     </mml:msub>
 314                                     <mml:mo>&it;</mml:mo>
 315                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 316                                     <mml:mi mathvariant="italic">R</mml:mi>
 317                                     </mml:msub>
 318                                     <mml:mo>-</mml:mo>
 319                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 320                                     <mml:mi mathvariant="italic">d</mml:mi>
 321                                     </mml:msub>
 322                                     <mml:mo>&it;</mml:mo>
 323                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 324                                     <mml:mi mathvariant="italic">R</mml:mi>
 325                                     </mml:msub>
 326                                 </mml:mrow>
 327                             </mml:mrow>
 328                         </mml:math></informalequation>
 329                         <informalequation><mml:math>
 330                             <!-- eqn: Gr  =    G sub s s sub G  -  G sub d d sub G : -->
 331                             <mml:mrow>
 332                                 <mml:mi mathvariant="italic">Gr</mml:mi>
 333                                 <mml:mo>=</mml:mo>
 334                                 <mml:mrow>
 335                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 336                                     <mml:mi mathvariant="italic">s</mml:mi>
 337                                     </mml:msub>
 338                                     <mml:mo>&it;</mml:mo>
 339                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 340                                     <mml:mi mathvariant="italic">G</mml:mi>
 341                                     </mml:msub>
 342                                     <mml:mo>-</mml:mo>
 343                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 344                                     <mml:mi mathvariant="italic">d</mml:mi>
 345                                     </mml:msub>
 346                                     <mml:mo>&it;</mml:mo>
 347                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 348                                     <mml:mi mathvariant="italic">G</mml:mi>
 349                                     </mml:msub>
 350                                 </mml:mrow>
 351                             </mml:mrow>
 352                         </mml:math></informalequation>
 353                         <informalequation><mml:math>
 354                             <!-- eqn: Br  =    B sub s s sub B  -  B sub d d sub B : -->
 355                             <mml:mrow>
 356                                 <mml:mi mathvariant="italic">Br</mml:mi>
 357                                 <mml:mo>=</mml:mo>
 358                                 <mml:mrow>
 359                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 360                                     <mml:mi mathvariant="italic">s</mml:mi>
 361                                     </mml:msub>
 362                                     <mml:mo>&it;</mml:mo>
 363                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 364                                     <mml:mi mathvariant="italic">B</mml:mi>
 365                                     </mml:msub>
 366                                     <mml:mo>-</mml:mo>
 367                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 368                                     <mml:mi mathvariant="italic">d</mml:mi>
 369                                     </mml:msub>
 370                                     <mml:mo>&it;</mml:mo>
 371                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 372                                     <mml:mi mathvariant="italic">B</mml:mi>
 373                                     </mml:msub>
 374                                 </mml:mrow>
 375                             </mml:mrow>
 376                         </mml:math></informalequation>
 377                         </entry>
 378                         <entry align="left">
 379                         <informalequation><mml:math>
 380                             <!-- eqn: Ar  =    A sub s s sub A  -  A sub d d sub A : -->
 381                             <mml:mrow>
 382                                 <mml:mi mathvariant="italic">Ar</mml:mi>
 383                                 <mml:mo>=</mml:mo>
 384                                 <mml:mrow>
 385                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 386                                     <mml:mi mathvariant="italic">s</mml:mi>
 387                                     </mml:msub>
 388                                     <mml:mo>&it;</mml:mo>
 389                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 390                                     <mml:mi mathvariant="italic">A</mml:mi>
 391                                     </mml:msub>
 392                                     <mml:mo>-</mml:mo>
 393                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 394                                     <mml:mi mathvariant="italic">d</mml:mi>
 395                                     </mml:msub>
 396                                     <mml:mo>&it;</mml:mo>
 397                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 398                                     <mml:mi mathvariant="italic">A</mml:mi>
 399                                     </mml:msub>
 400                                 </mml:mrow>
 401                             </mml:mrow>
 402                         </mml:math></informalequation>
 403                         </entry>
 404                     </row>
 405                     <row>
 406                         <entry align="left">
 407                         <constant>GL_FUNC_REVERSE_SUBTRACT</constant>
 408                         </entry>
 409                         <entry align="left">
 410                             <informalequation><mml:math>
 411                                 <!-- eqn: Rr  =      R sub d d sub R  -  R sub s s sub R : -->
 412                                 <mml:mrow>
 413                                     <mml:mi mathvariant="italic">Rr</mml:mi>
 414                                     <mml:mo>=</mml:mo>
 415                                     <mml:mrow>
 416                                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 417                                         <mml:mi mathvariant="italic">d</mml:mi>
 418                                         </mml:msub>
 419                                         <mml:mo>&it;</mml:mo>
 420                                         <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 421                                         <mml:mi mathvariant="italic">R</mml:mi>
 422                                         </mml:msub>
 423                                         <mml:mo>-</mml:mo>
 424                                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 425                                         <mml:mi mathvariant="italic">s</mml:mi>
 426                                         </mml:msub>
 427                                         <mml:mo>&it;</mml:mo>
 428                                         <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 429                                         <mml:mi mathvariant="italic">R</mml:mi>
 430                                         </mml:msub>
 431                                     </mml:mrow>
 432                                 </mml:mrow>
 433                             </mml:math></informalequation>
 434                             <informalequation><mml:math>
 435                                 <!-- eqn: Gr  =    G sub d d sub G  -  G sub s s sub G : -->
 436                                 <mml:mrow>
 437                                     <mml:mi mathvariant="italic">Gr</mml:mi>
 438                                     <mml:mo>=</mml:mo>
 439                                     <mml:mrow>
 440                                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 441                                         <mml:mi mathvariant="italic">d</mml:mi>
 442                                         </mml:msub>
 443                                         <mml:mo>&it;</mml:mo>
 444                                         <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 445                                         <mml:mi mathvariant="italic">G</mml:mi>
 446                                         </mml:msub>
 447                                         <mml:mo>-</mml:mo>
 448                                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 449                                         <mml:mi mathvariant="italic">s</mml:mi>
 450                                         </mml:msub>
 451                                         <mml:mo>&it;</mml:mo>
 452                                         <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 453                                         <mml:mi mathvariant="italic">G</mml:mi>
 454                                         </mml:msub>
 455                                     </mml:mrow>
 456                                 </mml:mrow>
 457                             </mml:math></informalequation>
 458                             <informalequation><mml:math>
 459                                 <!-- eqn: Br  =    B sub d d sub B  -  B sub s s sub B : -->
 460                                 <mml:mrow>
 461                                     <mml:mi mathvariant="italic">Br</mml:mi>
 462                                     <mml:mo>=</mml:mo>
 463                                     <mml:mrow>
 464                                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 465                                         <mml:mi mathvariant="italic">d</mml:mi>
 466                                         </mml:msub>
 467                                         <mml:mo>&it;</mml:mo>
 468                                         <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 469                                         <mml:mi mathvariant="italic">B</mml:mi>
 470                                         </mml:msub>
 471                                         <mml:mo>-</mml:mo>
 472                                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 473                                         <mml:mi mathvariant="italic">s</mml:mi>
 474                                         </mml:msub>
 475                                         <mml:mo>&it;</mml:mo>
 476                                         <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 477                                         <mml:mi mathvariant="italic">B</mml:mi>
 478                                         </mml:msub>
 479                                     </mml:mrow>
 480                                 </mml:mrow>
 481                             </mml:math></informalequation>
 482                         </entry>
 483                         <entry align="left">
 484                             <informalequation><mml:math>
 485                                 <!-- eqn: Ar  =    A sub d d sub A  -  A sub s s sub A : -->
 486                                 <mml:mrow>
 487                                     <mml:mi mathvariant="italic">Ar</mml:mi>
 488                                     <mml:mo>=</mml:mo>
 489                                     <mml:mrow>
 490                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 491                                         <mml:mi mathvariant="italic">d</mml:mi>
 492                                         </mml:msub>
 493                                         <mml:mo>&it;</mml:mo>
 494                                         <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 495                                         <mml:mi mathvariant="italic">A</mml:mi>
 496                                         </mml:msub>
 497                                         <mml:mo>-</mml:mo>
 498                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 499                                         <mml:mi mathvariant="italic">s</mml:mi>
 500                                         </mml:msub>
 501                                         <mml:mo>&it;</mml:mo>
 502                                         <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 503                                         <mml:mi mathvariant="italic">A</mml:mi>
 504                                         </mml:msub>
 505                                     </mml:mrow>
 506                                 </mml:mrow>
 507                             </mml:math></informalequation>
 508                         </entry>
 509                     </row>
 510                     <row>
 511                         <entry align="left">
 512                         <constant>GL_MIN</constant>
 513                         </entry>
 514                         <entry align="left">
 515                             <informalequation><mml:math>
 516                                 <!-- eqn: Rr  =      min ( R sub s, R sub d): -->
 517                                 <mml:mrow>
 518                                     <mml:mi mathvariant="italic">Rr</mml:mi>
 519                                     <mml:mo>=</mml:mo>
 520                                     <mml:mrow>
 521                                         <mml:mi mathvariant="italic">min</mml:mi>
 522                                         <mml:mo>&af;</mml:mo>
 523                                         <mml:mfenced open="(" close=")">
 524                                             <mml:mrow>
 525                                                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 526                                                 <mml:mi mathvariant="italic">s</mml:mi>
 527                                                 </mml:msub>
 528                                             </mml:mrow>
 529                                             <mml:mrow>
 530                                                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 531                                                 <mml:mi mathvariant="italic">d</mml:mi>
 532                                                 </mml:msub>
 533                                             </mml:mrow>
 534                                         </mml:mfenced>
 535                                     </mml:mrow>
 536                                 </mml:mrow>
 537                             </mml:math></informalequation>
 538                             <informalequation><mml:math>
 539                                 <!-- eqn: Gr  =      min ( G sub s, G sub d): -->
 540                                 <mml:mrow>
 541                                     <mml:mi mathvariant="italic">Gr</mml:mi>
 542                                     <mml:mo>=</mml:mo>
 543                                     <mml:mrow>
 544                                         <mml:mi mathvariant="italic">min</mml:mi>
 545                                         <mml:mo>&af;</mml:mo>
 546                                         <mml:mfenced open="(" close=")">
 547                                             <mml:mrow>
 548                                                 <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 549                                                 <mml:mi mathvariant="italic">s</mml:mi>
 550                                                 </mml:msub>
 551                                             </mml:mrow>
 552                                             <mml:mrow>
 553                                                 <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 554                                                 <mml:mi mathvariant="italic">d</mml:mi>
 555                                                 </mml:msub>
 556                                             </mml:mrow>
 557                                         </mml:mfenced>
 558                                     </mml:mrow>
 559                                 </mml:mrow>
 560                             </mml:math></informalequation>
 561                             <informalequation><mml:math>
 562                                 <!-- eqn: Br  =      min ( B sub s, B sub d): -->
 563                                 <mml:mrow>
 564                                     <mml:mi mathvariant="italic">Br</mml:mi>
 565                                     <mml:mo>=</mml:mo>
 566                                     <mml:mrow>
 567                                         <mml:mi mathvariant="italic">min</mml:mi>
 568                                         <mml:mo>&af;</mml:mo>
 569                                         <mml:mfenced open="(" close=")">
 570                                             <mml:mrow>
 571                                                 <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 572                                                 <mml:mi mathvariant="italic">s</mml:mi>
 573                                                 </mml:msub>
 574                                             </mml:mrow>
 575                                             <mml:mrow>
 576                                                 <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 577                                                 <mml:mi mathvariant="italic">d</mml:mi>
 578                                                 </mml:msub>
 579                                             </mml:mrow>
 580                                         </mml:mfenced>
 581                                     </mml:mrow>
 582                                 </mml:mrow>
 583                             </mml:math></informalequation>
 584                         </entry>
 585                         <entry align="left">
 586                             <informalequation><mml:math>
 587                                 <!-- eqn: Ar  =      min ( A sub s, A sub d): -->
 588                                 <mml:mrow>
 589                                     <mml:mi mathvariant="italic">Ar</mml:mi>
 590                                     <mml:mo>=</mml:mo>
 591                                     <mml:mrow>
 592                                         <mml:mi mathvariant="italic">min</mml:mi>
 593                                         <mml:mo>&af;</mml:mo>
 594                                         <mml:mfenced open="(" close=")">
 595                                             <mml:mrow>
 596                                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 597                                                 <mml:mi mathvariant="italic">s</mml:mi>
 598                                                 </mml:msub>
 599                                             </mml:mrow>
 600                                             <mml:mrow>
 601                                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 602                                                 <mml:mi mathvariant="italic">d</mml:mi>
 603                                                 </mml:msub>
 604                                             </mml:mrow>
 605                                         </mml:mfenced>
 606                                     </mml:mrow>
 607                                 </mml:mrow>
 608                             </mml:math></informalequation>
 609                         </entry>
 610                     </row>
 611                     <row>
 612                         <entry align="left">
 613                         <constant>GL_MAX</constant>
 614                         </entry>
 615                         <entry align="left">
 616                             <informalequation><mml:math>
 617                                 <!-- eqn: Rr  =      max ( R sub s, R sub d): -->
 618                                 <mml:mrow>
 619                                     <mml:mi mathvariant="italic">Rr</mml:mi>
 620                                     <mml:mo>=</mml:mo>
 621                                     <mml:mrow>
 622                                         <mml:mi mathvariant="italic">max</mml:mi>
 623                                         <mml:mo>&af;</mml:mo>
 624                                         <mml:mfenced open="(" close=")">
 625                                             <mml:mrow>
 626                                                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 627                                                 <mml:mi mathvariant="italic">s</mml:mi>
 628                                                 </mml:msub>
 629                                             </mml:mrow>
 630                                             <mml:mrow>
 631                                                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 632                                                 <mml:mi mathvariant="italic">d</mml:mi>
 633                                                 </mml:msub>
 634                                             </mml:mrow>
 635                                         </mml:mfenced>
 636                                     </mml:mrow>
 637                                 </mml:mrow>
 638                             </mml:math></informalequation>
 639                             <informalequation><mml:math>
 640                                 <!-- eqn: Gr  =      max ( G sub s, G sub d): -->
 641                                 <mml:mrow>
 642                                     <mml:mi mathvariant="italic">Gr</mml:mi>
 643                                     <mml:mo>=</mml:mo>
 644                                     <mml:mrow>
 645                                         <mml:mi mathvariant="italic">max</mml:mi>
 646                                         <mml:mo>&af;</mml:mo>
 647                                         <mml:mfenced open="(" close=")">
 648                                             <mml:mrow>
 649                                                 <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 650                                                 <mml:mi mathvariant="italic">s</mml:mi>
 651                                                 </mml:msub>
 652                                             </mml:mrow>
 653                                             <mml:mrow>
 654                                                 <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 655                                                 <mml:mi mathvariant="italic">d</mml:mi>
 656                                                 </mml:msub>
 657                                             </mml:mrow>
 658                                         </mml:mfenced>
 659                                     </mml:mrow>
 660                                 </mml:mrow>
 661                             </mml:math></informalequation>
 662                             <informalequation><mml:math>
 663                                 <!-- eqn: Br  =      max ( B sub s, B sub d): -->
 664                                 <mml:mrow>
 665                                     <mml:mi mathvariant="italic">Br</mml:mi>
 666                                     <mml:mo>=</mml:mo>
 667                                     <mml:mrow>
 668                                         <mml:mi mathvariant="italic">max</mml:mi>
 669                                         <mml:mo>&af;</mml:mo>
 670                                         <mml:mfenced open="(" close=")">
 671                                             <mml:mrow>
 672                                                 <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 673                                                 <mml:mi mathvariant="italic">s</mml:mi>
 674                                                 </mml:msub>
 675                                             </mml:mrow>
 676                                             <mml:mrow>
 677                                                 <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 678                                                 <mml:mi mathvariant="italic">d</mml:mi>
 679                                                 </mml:msub>
 680                                             </mml:mrow>
 681                                         </mml:mfenced>
 682                                     </mml:mrow>
 683                                 </mml:mrow>
 684                             </mml:math></informalequation>
 685                         </entry>
 686                         <entry align="left">
 687                             <informalequation><mml:math>
 688                                 <!-- eqn: Ar  =      max ( A sub s, A sub d): -->
 689                                 <mml:mrow>
 690                                     <mml:mi mathvariant="italic">Ar</mml:mi>
 691                                     <mml:mo>=</mml:mo>
 692                                     <mml:mrow>
 693                                         <mml:mi mathvariant="italic">max</mml:mi>
 694                                         <mml:mo>&af;</mml:mo>
 695                                         <mml:mfenced open="(" close=")">
 696                                             <mml:mrow>
 697                                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 698                                                 <mml:mi mathvariant="italic">s</mml:mi>
 699                                                 </mml:msub>
 700                                             </mml:mrow>
 701                                             <mml:mrow>
 702                                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 703                                                 <mml:mi mathvariant="italic">d</mml:mi>
 704                                                 </mml:msub>
 705                                             </mml:mrow>
 706                                         </mml:mfenced>
 707                                     </mml:mrow>
 708                                 </mml:mrow>
 709                             </mml:math></informalequation>
 710                         </entry>
 711                     </row>
 712                 </tbody>
 713             </tgroup>
 714         </informaltable>
 715         </para>
 716         <para>
 717             The results of these equations are clamped to the range
 718                         <inlineequation><mml:math>
 719                             <!-- eqn: [0,1]: -->
 720                             <mml:mfenced open="[" close="]">
 721                                 <mml:mn>0</mml:mn>
 722                                 <mml:mn>1</mml:mn>
 723                             </mml:mfenced>
 724                         </mml:math></inlineequation>.
 725         </para>
 726         <para>
 727             The <constant>GL_MIN</constant> and <constant>GL_MAX</constant> equations are useful for applications
 728             that analyze image data (image thresholding against a constant color,
 729             for example).
 730             The <constant>GL_FUNC_ADD</constant> equation is useful
 731             for antialiasing and transparency, among other things.
 732         </para>
 733         <para>
 734             Initially, both the RGB blend equation and the alpha blend equation are set to <constant>GL_FUNC_ADD</constant>.
 735         </para>
 736         <para>
 737         </para>
 738     </refsect1>
 739     <refsect1 id="notes"><title>Notes</title>
 740         <para>
 741             The <constant>GL_MIN</constant>, and <constant>GL_MAX</constant> equations do not use
 742             the source or destination factors, only the source and destination colors.
 743         </para>
 744     </refsect1>
 745     <refsect1 id="errors"><title>Errors</title>
 746         <para>
 747             <constant>GL_INVALID_ENUM</constant> is generated if <parameter>mode</parameter> is not one of
 748             <constant>GL_FUNC_ADD</constant>, <constant>GL_FUNC_SUBTRACT</constant>, <constant>GL_FUNC_REVERSE_SUBTRACT</constant>,
 749             <constant>GL_MAX</constant>, or <constant>GL_MIN</constant>.
 750         </para>
 751         <para>
 752             <constant>GL_INVALID_VALUE</constant> is generated by <function>glBlendEquationi</function> if <parameter>buf</parameter> is greater
 753             than or equal to the value of <constant>GL_MAX_DRAW_BUFFERS</constant>.
 754         </para>
 755     </refsect1>
 756     <refsect1 id="associatedgets"><title>Associated Gets</title>
 757          <para>
 758             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_BLEND_EQUATION_RGB</constant>
 759          </para>
 760          <para>
 761             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with an argument of <constant>GL_BLEND_EQUATION_ALPHA</constant>
 762          </para>
 763     </refsect1>
 764     <refsect1 id="seealso"><title>See Also</title>
 765         <para>
 766             <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry>,
 767             <citerefentry><refentrytitle>glBlendFunc</refentrytitle></citerefentry>
 768             <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>
 769         </para>
 770     </refsect1>
 771     <refsect1 id="Copyright"><title>Copyright</title>
 772         <para>
 773             Copyright <trademark class="copyright"></trademark> 1991-2006
 774             Silicon Graphics, Inc. This document is licensed under the SGI
 775             Free Software B License. For details, see
 776             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
 777         </para>
 778     </refsect1>
 779 </refentry>