upstream-doc/man2/glBlendFunc.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="glBlendFunc">
   5     <refmeta>
   6         <refmetainfo>
   7             <copyright>
   8                 <year>1991-2006</year>
   9                 <holder>Silicon Graphics, Inc.</holder>
  10             </copyright>
  11         </refmetainfo>
  12         <refentrytitle>glBlendFunc</refentrytitle>
  13         <manvolnum>3G</manvolnum>
  14     </refmeta>
  15     <refnamediv>
  16         <refname>glBlendFunc</refname>
  17         <refpurpose>specify pixel arithmetic</refpurpose>
  18     </refnamediv>
  19     <refsynopsisdiv><title>C Specification</title>
  20         <funcsynopsis>
  21             <funcprototype>
  22                 <funcdef>void <function>glBlendFunc</function></funcdef>
  23                 <paramdef>GLenum <parameter>sfactor</parameter></paramdef>
  24                 <paramdef>GLenum <parameter>dfactor</parameter></paramdef>
  25             </funcprototype>
  26         </funcsynopsis>
  27     </refsynopsisdiv>
  28     <!-- eqn: ignoring delim $$ -->
  29     <refsect1 id="parameters"><title>Parameters</title>
  30         <variablelist>
  31         <varlistentry>
  32             <term><parameter>sfactor</parameter></term>
  33             <listitem>
  34                 <para>
  35                     Specifies how the red, green, blue,
  36                     and alpha source blending factors are computed.
  37                     The following symbolic constants are accepted:
  38                     <constant>GL_ZERO</constant>,
  39                     <constant>GL_ONE</constant>,
  40                     <constant>GL_SRC_COLOR</constant>,
  41                     <constant>GL_ONE_MINUS_SRC_COLOR</constant>,
  42                     <constant>GL_DST_COLOR</constant>,
  43                     <constant>GL_ONE_MINUS_DST_COLOR</constant>,
  44                     <constant>GL_SRC_ALPHA</constant>,
  45                     <constant>GL_ONE_MINUS_SRC_ALPHA</constant>,
  46                     <constant>GL_DST_ALPHA</constant>,
  47                     <constant>GL_ONE_MINUS_DST_ALPHA</constant>,
  48                     <constant>GL_CONSTANT_COLOR</constant>,
  49                     <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>,
  50                     <constant>GL_CONSTANT_ALPHA</constant>,
  51                     <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>, and
  52                     <constant>GL_SRC_ALPHA_SATURATE</constant>.
  53                     The initial value is <constant>GL_ONE</constant>.
  54                 </para>
  55             </listitem>
  56         </varlistentry>
  57         <varlistentry>
  58             <term><parameter>dfactor</parameter></term>
  59             <listitem>
  60                 <para>
  61                     Specifies how the red, green, blue,
  62                     and alpha destination blending factors are computed.
  63                     The following symbolic constants are accepted:
  64                     <constant>GL_ZERO</constant>,
  65                     <constant>GL_ONE</constant>,
  66                     <constant>GL_SRC_COLOR</constant>,
  67                     <constant>GL_ONE_MINUS_SRC_COLOR</constant>,
  68                     <constant>GL_DST_COLOR</constant>,
  69                     <constant>GL_ONE_MINUS_DST_COLOR</constant>,
  70                     <constant>GL_SRC_ALPHA</constant>,
  71                     <constant>GL_ONE_MINUS_SRC_ALPHA</constant>,
  72                     <constant>GL_DST_ALPHA</constant>,
  73                     <constant>GL_ONE_MINUS_DST_ALPHA</constant>.
  74                     <constant>GL_CONSTANT_COLOR</constant>,
  75                     <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>,
  76                     <constant>GL_CONSTANT_ALPHA</constant>, and
  77                     <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>.
  78                     The initial value is <constant>GL_ZERO</constant>.
  79                 </para>
  80             </listitem>
  81         </varlistentry>
  82         </variablelist>
  83     </refsect1>
  84     <refsect1 id="description"><title>Description</title>
  85         <para>
  86             In RGBA mode, pixels can be drawn using a function that blends
  87             the incoming (source) RGBA values with the RGBA values
  88             that are already in the frame buffer (the destination values).
  89             Blending is initially disabled.
  90             Use <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant>
  91             to enable and disable blending.
  92         </para>
  93         <para>
  94             <function>glBlendFunc</function> defines the operation of blending when it is enabled.
  95             <parameter>sfactor</parameter> specifies which method is used to scale the
  96             source color components.
  97             <parameter>dfactor</parameter> specifies which method is used to scale the
  98             destination color components.
  99             The possible methods are described in the following table.
 100             Each method defines four scale factors,
 101             one each for red, green, blue, and alpha.
 102             In the table and in subsequent equations, source and destination
 103             color components are referred to as
 104             <inlineequation><mml:math>
 105                 <!-- eqn: ( R sub s , G sub s , B sub s , A sub s ):-->
 106                 <mml:mfenced open="(" close=")">
 107                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 108                     <mml:mi mathvariant="italic">s</mml:mi>
 109                     </mml:msub>
 110                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 111                     <mml:mi mathvariant="italic">s</mml:mi>
 112                     </mml:msub>
 113                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 114                     <mml:mi mathvariant="italic">s</mml:mi>
 115                     </mml:msub>
 116                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 117                     <mml:mi mathvariant="italic">s</mml:mi>
 118                     </mml:msub>
 119                 </mml:mfenced>
 120             </mml:math></inlineequation>
 121             and
 122             <inlineequation><mml:math>
 123                 <!-- eqn: ( R sub d , G sub d , B sub d , A sub d ):-->
 124                 <mml:mfenced open="(" close=")">
 125                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 126                     <mml:mi mathvariant="italic">d</mml:mi>
 127                     </mml:msub>
 128                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 129                     <mml:mi mathvariant="italic">d</mml:mi>
 130                     </mml:msub>
 131                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 132                     <mml:mi mathvariant="italic">d</mml:mi>
 133                     </mml:msub>
 134                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 135                     <mml:mi mathvariant="italic">d</mml:mi>
 136                     </mml:msub>
 137                 </mml:mfenced>
 138             </mml:math></inlineequation>.
 139             The color specified by <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry> is referred to as
 140             <inlineequation><mml:math>
 141                 <!-- eqn: ( R sub c , G sub c , B sub c , A sub c ):-->
 142                 <mml:mfenced open="(" close=")">
 143                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 144                     <mml:mi mathvariant="italic">c</mml:mi>
 145                     </mml:msub>
 146                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 147                     <mml:mi mathvariant="italic">c</mml:mi>
 148                     </mml:msub>
 149                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 150                     <mml:mi mathvariant="italic">c</mml:mi>
 151                     </mml:msub>
 152                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 153                     <mml:mi mathvariant="italic">c</mml:mi>
 154                     </mml:msub>
 155                 </mml:mfenced>
 156             </mml:math></inlineequation>.
 157             They are understood to have integer values between 0 and
 158             <inlineequation><mml:math>
 159                 <!-- eqn: ( k sub R , k sub G , k sub B , k sub A ):-->
 160                 <mml:mfenced open="(" close=")">
 161                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 162                     <mml:mi mathvariant="italic">R</mml:mi>
 163                     </mml:msub>
 164                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 165                     <mml:mi mathvariant="italic">G</mml:mi>
 166                     </mml:msub>
 167                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 168                     <mml:mi mathvariant="italic">B</mml:mi>
 169                     </mml:msub>
 170                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 171                     <mml:mi mathvariant="italic">A</mml:mi>
 172                     </mml:msub>
 173                 </mml:mfenced>
 174             </mml:math></inlineequation>,
 175             where
 176         </para>
 177         <para>
 178             <para>
 179                 <inlineequation><mml:math>
 180                     <!-- eqn: k sub c  =  2 sup {m sub c} - 1:-->
 181                     <mml:mrow>
 182                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 183                         <mml:mi mathvariant="italic">c</mml:mi>
 184                         </mml:msub>
 185                         <mml:mo>=</mml:mo>
 186                         <mml:mrow>
 187                             <mml:msup><mml:mn>2</mml:mn>
 188                             <mml:mfenced open="" close="">
 189                                 <mml:msub><mml:mi mathvariant="italic">m</mml:mi>
 190                                 <mml:mi mathvariant="italic">c</mml:mi>
 191                                 </mml:msub>
 192                             </mml:mfenced>
 193                             </mml:msup>
 194                             <mml:mo>-</mml:mo>
 195                             <mml:mn>1</mml:mn>
 196                         </mml:mrow>
 197                     </mml:mrow>
 198                 </mml:math></inlineequation>
 199             </para>
 200         </para>
 201         <para>
 202             and
 203             <inlineequation><mml:math>
 204                 <!-- eqn: ( m sub R , m sub G , m sub B , m sub A ):-->
 205                 <mml:mfenced open="(" close=")">
 206                     <mml:msub><mml:mi mathvariant="italic">m</mml:mi>
 207                     <mml:mi mathvariant="italic">R</mml:mi>
 208                     </mml:msub>
 209                     <mml:msub><mml:mi mathvariant="italic">m</mml:mi>
 210                     <mml:mi mathvariant="italic">G</mml:mi>
 211                     </mml:msub>
 212                     <mml:msub><mml:mi mathvariant="italic">m</mml:mi>
 213                     <mml:mi mathvariant="italic">B</mml:mi>
 214                     </mml:msub>
 215                     <mml:msub><mml:mi mathvariant="italic">m</mml:mi>
 216                     <mml:mi mathvariant="italic">A</mml:mi>
 217                     </mml:msub>
 218                 </mml:mfenced>
 219             </mml:math></inlineequation>
 220             is the number of red,
 221             green,
 222             blue,
 223             and alpha bitplanes.
 224         </para>
 225         <para>
 226             Source and destination scale factors are referred to as
 227             <inlineequation><mml:math>
 228                 <!-- eqn: ( s sub R , s sub G , s sub B , s sub A ):-->
 229                 <mml:mfenced open="(" close=")">
 230                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 231                     <mml:mi mathvariant="italic">R</mml:mi>
 232                     </mml:msub>
 233                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 234                     <mml:mi mathvariant="italic">G</mml:mi>
 235                     </mml:msub>
 236                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 237                     <mml:mi mathvariant="italic">B</mml:mi>
 238                     </mml:msub>
 239                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 240                     <mml:mi mathvariant="italic">A</mml:mi>
 241                     </mml:msub>
 242                 </mml:mfenced>
 243             </mml:math></inlineequation>
 244             and
 245             <inlineequation><mml:math>
 246                 <!-- eqn: ( d sub R , d sub G , d sub B , d sub A ):-->
 247                 <mml:mfenced open="(" close=")">
 248                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 249                     <mml:mi mathvariant="italic">R</mml:mi>
 250                     </mml:msub>
 251                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 252                     <mml:mi mathvariant="italic">G</mml:mi>
 253                     </mml:msub>
 254                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 255                     <mml:mi mathvariant="italic">B</mml:mi>
 256                     </mml:msub>
 257                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 258                     <mml:mi mathvariant="italic">A</mml:mi>
 259                     </mml:msub>
 260                 </mml:mfenced>
 261             </mml:math></inlineequation>.
 262             The scale factors described in the table,
 263             denoted
 264             <inlineequation><mml:math>
 265                 <!-- eqn: ( f sub R , f sub G , f sub B , f sub A ):-->
 266                 <mml:mfenced open="(" close=")">
 267                     <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 268                     <mml:mi mathvariant="italic">R</mml:mi>
 269                     </mml:msub>
 270                     <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 271                     <mml:mi mathvariant="italic">G</mml:mi>
 272                     </mml:msub>
 273                     <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 274                     <mml:mi mathvariant="italic">B</mml:mi>
 275                     </mml:msub>
 276                     <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 277                     <mml:mi mathvariant="italic">A</mml:mi>
 278                     </mml:msub>
 279                 </mml:mfenced>
 280             </mml:math></inlineequation>,
 281             represent either source or destination factors.
 282             All scale factors have range
 283             <inlineequation><mml:math>
 284                 <!-- eqn: [0,1]:-->
 285                 <mml:mfenced open="[" close="]">
 286                     <mml:mn>0</mml:mn>
 287                     <mml:mn>1</mml:mn>
 288                 </mml:mfenced>
 289             </mml:math></inlineequation>.
 290         </para>
 291         <para>
 292         </para>
 293         <informaltable frame="topbot">
 294             <tgroup cols="2" align="left">
 295                 <colspec/>
 296                 <colspec/>
 297                 <thead>
 298                     <row>
 299                         <entry rowsep="1" align="left"><emphasis role="bold">
 300                         Parameter
 301                         </emphasis></entry>
 302                         <entry rowsep="1" align="left"><emphasis role="bold">
 303                         <inlineequation><mml:math>
 304                             <!-- eqn: ( f sub R ,    f sub G ,    f sub B ,    f sub A ):-->
 305                             <mml:mfenced open="(" close=")">
 306                                 <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 307                                 <mml:mi mathvariant="italic">R</mml:mi>
 308                                 </mml:msub>
 309                                 <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 310                                 <mml:mi mathvariant="italic">G</mml:mi>
 311                                 </mml:msub>
 312                                 <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 313                                 <mml:mi mathvariant="italic">B</mml:mi>
 314                                 </mml:msub>
 315                                 <mml:msub><mml:mi mathvariant="italic">f</mml:mi>
 316                                 <mml:mi mathvariant="italic">A</mml:mi>
 317                                 </mml:msub>
 318                             </mml:mfenced>
 319                         </mml:math></inlineequation>
 320                         </emphasis></entry>
 321                     </row>
 322                 </thead>
 323                 <tbody>
 324                     <row>
 325                         <entry align="left">
 326                         <constant>GL_ZERO</constant>
 327                         </entry>
 328                         <entry align="left">
 329                         <inlineequation><mml:math>
 330                             <!-- eqn: ( 0,  0,  0,  0 ):-->
 331                             <mml:mfenced open="(" close=")">
 332                                 <mml:mn>0</mml:mn>
 333                                 <mml:mn>0</mml:mn>
 334                                 <mml:mn>0</mml:mn>
 335                                 <mml:mn>0</mml:mn>
 336                             </mml:mfenced>
 337                         </mml:math></inlineequation>
 338                         </entry>
 339                     </row>
 340                     <row>
 341                         <entry align="left">
 342                         <constant>GL_ONE</constant>
 343                         </entry>
 344                         <entry align="left">
 345                         <inlineequation><mml:math>
 346                             <!-- eqn: ( 1,  1,  1,  1 ):-->
 347                             <mml:mfenced open="(" close=")">
 348                                 <mml:mn>1</mml:mn>
 349                                 <mml:mn>1</mml:mn>
 350                                 <mml:mn>1</mml:mn>
 351                                 <mml:mn>1</mml:mn>
 352                             </mml:mfenced>
 353                         </mml:math></inlineequation>
 354                         </entry>
 355                     </row>
 356                     <row>
 357                         <entry align="left">
 358                         <constant>GL_SRC_COLOR</constant>
 359                         </entry>
 360                         <entry align="left">
 361                         <inlineequation><mml:math>
 362                             <!-- eqn: ( R sub s / k sub R ,  G sub s / k sub G ,  B sub s / k sub B ,  A sub s / k sub A ):-->
 363                             <mml:mfenced open="(" close=")">
 364                                 <mml:mfrac>
 365                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 366                                     <mml:mi mathvariant="italic">s</mml:mi>
 367                                     </mml:msub>
 368                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 369                                     <mml:mi mathvariant="italic">R</mml:mi>
 370                                     </mml:msub>
 371                                 </mml:mfrac>
 372                                 <mml:mfrac>
 373                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 374                                     <mml:mi mathvariant="italic">s</mml:mi>
 375                                     </mml:msub>
 376                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 377                                     <mml:mi mathvariant="italic">G</mml:mi>
 378                                     </mml:msub>
 379                                 </mml:mfrac>
 380                                 <mml:mfrac>
 381                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 382                                     <mml:mi mathvariant="italic">s</mml:mi>
 383                                     </mml:msub>
 384                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 385                                     <mml:mi mathvariant="italic">B</mml:mi>
 386                                     </mml:msub>
 387                                 </mml:mfrac>
 388                                 <mml:mfrac>
 389                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 390                                     <mml:mi mathvariant="italic">s</mml:mi>
 391                                     </mml:msub>
 392                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 393                                     <mml:mi mathvariant="italic">A</mml:mi>
 394                                     </mml:msub>
 395                                 </mml:mfrac>
 396                             </mml:mfenced>
 397                         </mml:math></inlineequation>
 398                         </entry>
 399                     </row>
 400                     <row>
 401                         <entry align="left">
 402                         <constant>GL_ONE_MINUS_SRC_COLOR</constant>
 403                         </entry>
 404                         <entry align="left">
 405                         <inlineequation><mml:math>
 406                             <!-- eqn: ( 1,  1,  1,  1 )  -  (R sub s / k sub R ,  G sub s / k sub G ,  B sub s / k sub B ,  A sub s / k sub A ):-->
 407                             <mml:mrow>
 408                                 <mml:mfenced open="(" close=")">
 409                                     <mml:mn>1</mml:mn>
 410                                     <mml:mn>1</mml:mn>
 411                                     <mml:mn>1</mml:mn>
 412                                     <mml:mn>1</mml:mn>
 413                                 </mml:mfenced>
 414                                 <mml:mo>-</mml:mo>
 415                                 <mml:mfenced open="(" close=")">
 416                                     <mml:mfrac>
 417                                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 418                                         <mml:mi mathvariant="italic">s</mml:mi>
 419                                         </mml:msub>
 420                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 421                                         <mml:mi mathvariant="italic">R</mml:mi>
 422                                         </mml:msub>
 423                                     </mml:mfrac>
 424                                     <mml:mfrac>
 425                                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 426                                         <mml:mi mathvariant="italic">s</mml:mi>
 427                                         </mml:msub>
 428                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 429                                         <mml:mi mathvariant="italic">G</mml:mi>
 430                                         </mml:msub>
 431                                     </mml:mfrac>
 432                                     <mml:mfrac>
 433                                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 434                                         <mml:mi mathvariant="italic">s</mml:mi>
 435                                         </mml:msub>
 436                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 437                                         <mml:mi mathvariant="italic">B</mml:mi>
 438                                         </mml:msub>
 439                                     </mml:mfrac>
 440                                     <mml:mfrac>
 441                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 442                                         <mml:mi mathvariant="italic">s</mml:mi>
 443                                         </mml:msub>
 444                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 445                                         <mml:mi mathvariant="italic">A</mml:mi>
 446                                         </mml:msub>
 447                                     </mml:mfrac>
 448                                 </mml:mfenced>
 449                             </mml:mrow>
 450                         </mml:math></inlineequation>
 451                         </entry>
 452                     </row>
 453                     <row>
 454                         <entry align="left">
 455                         <constant>GL_DST_COLOR</constant>
 456                         </entry>
 457                         <entry align="left">
 458                         <inlineequation><mml:math>
 459                             <!-- eqn: ( R sub d / k sub R ,  G sub d / k sub G ,  B sub d / k sub B ,  A sub d / k sub A ):-->
 460                             <mml:mfenced open="(" close=")">
 461                                 <mml:mfrac>
 462                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 463                                     <mml:mi mathvariant="italic">d</mml:mi>
 464                                     </mml:msub>
 465                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 466                                     <mml:mi mathvariant="italic">R</mml:mi>
 467                                     </mml:msub>
 468                                 </mml:mfrac>
 469                                 <mml:mfrac>
 470                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 471                                     <mml:mi mathvariant="italic">d</mml:mi>
 472                                     </mml:msub>
 473                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 474                                     <mml:mi mathvariant="italic">G</mml:mi>
 475                                     </mml:msub>
 476                                 </mml:mfrac>
 477                                 <mml:mfrac>
 478                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 479                                     <mml:mi mathvariant="italic">d</mml:mi>
 480                                     </mml:msub>
 481                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 482                                     <mml:mi mathvariant="italic">B</mml:mi>
 483                                     </mml:msub>
 484                                 </mml:mfrac>
 485                                 <mml:mfrac>
 486                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 487                                     <mml:mi mathvariant="italic">d</mml:mi>
 488                                     </mml:msub>
 489                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 490                                     <mml:mi mathvariant="italic">A</mml:mi>
 491                                     </mml:msub>
 492                                 </mml:mfrac>
 493                             </mml:mfenced>
 494                         </mml:math></inlineequation>
 495                         </entry>
 496                     </row>
 497                     <row>
 498                         <entry align="left">
 499                         <constant>GL_ONE_MINUS_DST_COLOR</constant>
 500                         </entry>
 501                         <entry align="left">
 502                         <inlineequation><mml:math>
 503                             <!-- eqn: ( 1,  1,  1,  1 )  -  (R sub d / k sub R ,  G sub d / k sub G ,  B sub d / k sub B ,  A sub d / k sub A ):-->
 504                             <mml:mrow>
 505                                 <mml:mfenced open="(" close=")">
 506                                     <mml:mn>1</mml:mn>
 507                                     <mml:mn>1</mml:mn>
 508                                     <mml:mn>1</mml:mn>
 509                                     <mml:mn>1</mml:mn>
 510                                 </mml:mfenced>
 511                                 <mml:mo>-</mml:mo>
 512                                 <mml:mfenced open="(" close=")">
 513                                     <mml:mfrac>
 514                                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 515                                         <mml:mi mathvariant="italic">d</mml:mi>
 516                                         </mml:msub>
 517                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 518                                         <mml:mi mathvariant="italic">R</mml:mi>
 519                                         </mml:msub>
 520                                     </mml:mfrac>
 521                                     <mml:mfrac>
 522                                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 523                                         <mml:mi mathvariant="italic">d</mml:mi>
 524                                         </mml:msub>
 525                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 526                                         <mml:mi mathvariant="italic">G</mml:mi>
 527                                         </mml:msub>
 528                                     </mml:mfrac>
 529                                     <mml:mfrac>
 530                                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 531                                         <mml:mi mathvariant="italic">d</mml:mi>
 532                                         </mml:msub>
 533                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 534                                         <mml:mi mathvariant="italic">B</mml:mi>
 535                                         </mml:msub>
 536                                     </mml:mfrac>
 537                                     <mml:mfrac>
 538                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 539                                         <mml:mi mathvariant="italic">d</mml:mi>
 540                                         </mml:msub>
 541                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 542                                         <mml:mi mathvariant="italic">A</mml:mi>
 543                                         </mml:msub>
 544                                     </mml:mfrac>
 545                                 </mml:mfenced>
 546                             </mml:mrow>
 547                         </mml:math></inlineequation>
 548                         </entry>
 549                     </row>
 550                     <row>
 551                         <entry align="left">
 552                         <constant>GL_SRC_ALPHA</constant>
 553                         </entry>
 554                         <entry align="left">
 555                         <inlineequation><mml:math>
 556                             <!-- eqn: ( A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ):-->
 557                             <mml:mfenced open="(" close=")">
 558                                 <mml:mfrac>
 559                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 560                                     <mml:mi mathvariant="italic">s</mml:mi>
 561                                     </mml:msub>
 562                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 563                                     <mml:mi mathvariant="italic">A</mml:mi>
 564                                     </mml:msub>
 565                                 </mml:mfrac>
 566                                 <mml:mfrac>
 567                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 568                                     <mml:mi mathvariant="italic">s</mml:mi>
 569                                     </mml:msub>
 570                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 571                                     <mml:mi mathvariant="italic">A</mml:mi>
 572                                     </mml:msub>
 573                                 </mml:mfrac>
 574                                 <mml:mfrac>
 575                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 576                                     <mml:mi mathvariant="italic">s</mml:mi>
 577                                     </mml:msub>
 578                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 579                                     <mml:mi mathvariant="italic">A</mml:mi>
 580                                     </mml:msub>
 581                                 </mml:mfrac>
 582                                 <mml:mfrac>
 583                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 584                                     <mml:mi mathvariant="italic">s</mml:mi>
 585                                     </mml:msub>
 586                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 587                                     <mml:mi mathvariant="italic">A</mml:mi>
 588                                     </mml:msub>
 589                                 </mml:mfrac>
 590                             </mml:mfenced>
 591                         </mml:math></inlineequation>
 592                         </entry>
 593                     </row>
 594                     <row>
 595                         <entry align="left">
 596                         <constant>GL_ONE_MINUS_SRC_ALPHA</constant>
 597                         </entry>
 598                         <entry align="left">
 599                         <inlineequation><mml:math>
 600                             <!-- eqn: ( 1,  1,  1,  1 )  -  (A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ,  A sub s / k sub A ):-->
 601                             <mml:mrow>
 602                                 <mml:mfenced open="(" close=")">
 603                                     <mml:mn>1</mml:mn>
 604                                     <mml:mn>1</mml:mn>
 605                                     <mml:mn>1</mml:mn>
 606                                     <mml:mn>1</mml:mn>
 607                                 </mml:mfenced>
 608                                 <mml:mo>-</mml:mo>
 609                                 <mml:mfenced open="(" close=")">
 610                                     <mml:mfrac>
 611                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 612                                         <mml:mi mathvariant="italic">s</mml:mi>
 613                                         </mml:msub>
 614                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 615                                         <mml:mi mathvariant="italic">A</mml:mi>
 616                                         </mml:msub>
 617                                     </mml:mfrac>
 618                                     <mml:mfrac>
 619                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 620                                         <mml:mi mathvariant="italic">s</mml:mi>
 621                                         </mml:msub>
 622                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 623                                         <mml:mi mathvariant="italic">A</mml:mi>
 624                                         </mml:msub>
 625                                     </mml:mfrac>
 626                                     <mml:mfrac>
 627                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 628                                         <mml:mi mathvariant="italic">s</mml:mi>
 629                                         </mml:msub>
 630                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 631                                         <mml:mi mathvariant="italic">A</mml:mi>
 632                                         </mml:msub>
 633                                     </mml:mfrac>
 634                                     <mml:mfrac>
 635                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 636                                         <mml:mi mathvariant="italic">s</mml:mi>
 637                                         </mml:msub>
 638                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 639                                         <mml:mi mathvariant="italic">A</mml:mi>
 640                                         </mml:msub>
 641                                     </mml:mfrac>
 642                                 </mml:mfenced>
 643                             </mml:mrow>
 644                         </mml:math></inlineequation>
 645                         </entry>
 646                     </row>
 647                     <row>
 648                         <entry align="left">
 649                         <constant>GL_DST_ALPHA</constant>
 650                         </entry>
 651                         <entry align="left">
 652                         <inlineequation><mml:math>
 653                             <!-- eqn: ( A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ):-->
 654                             <mml:mfenced open="(" close=")">
 655                                 <mml:mfrac>
 656                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 657                                     <mml:mi mathvariant="italic">d</mml:mi>
 658                                     </mml:msub>
 659                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 660                                     <mml:mi mathvariant="italic">A</mml:mi>
 661                                     </mml:msub>
 662                                 </mml:mfrac>
 663                                 <mml:mfrac>
 664                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 665                                     <mml:mi mathvariant="italic">d</mml:mi>
 666                                     </mml:msub>
 667                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 668                                     <mml:mi mathvariant="italic">A</mml:mi>
 669                                     </mml:msub>
 670                                 </mml:mfrac>
 671                                 <mml:mfrac>
 672                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 673                                     <mml:mi mathvariant="italic">d</mml:mi>
 674                                     </mml:msub>
 675                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 676                                     <mml:mi mathvariant="italic">A</mml:mi>
 677                                     </mml:msub>
 678                                 </mml:mfrac>
 679                                 <mml:mfrac>
 680                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 681                                     <mml:mi mathvariant="italic">d</mml:mi>
 682                                     </mml:msub>
 683                                     <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 684                                     <mml:mi mathvariant="italic">A</mml:mi>
 685                                     </mml:msub>
 686                                 </mml:mfrac>
 687                             </mml:mfenced>
 688                         </mml:math></inlineequation>
 689                         </entry>
 690                     </row>
 691                     <row>
 692                         <entry align="left">
 693                         <constant>GL_ONE_MINUS_DST_ALPHA</constant>
 694                         </entry>
 695                         <entry align="left">
 696                         <inlineequation><mml:math>
 697                             <!-- eqn: ( 1,  1,  1,  1 )  -  ( A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ,  A sub d / k sub A ):-->
 698                             <mml:mrow>
 699                                 <mml:mfenced open="(" close=")">
 700                                     <mml:mn>1</mml:mn>
 701                                     <mml:mn>1</mml:mn>
 702                                     <mml:mn>1</mml:mn>
 703                                     <mml:mn>1</mml:mn>
 704                                 </mml:mfenced>
 705                                 <mml:mo>-</mml:mo>
 706                                 <mml:mfenced open="(" close=")">
 707                                     <mml:mfrac>
 708                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 709                                         <mml:mi mathvariant="italic">d</mml:mi>
 710                                         </mml:msub>
 711                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 712                                         <mml:mi mathvariant="italic">A</mml:mi>
 713                                         </mml:msub>
 714                                     </mml:mfrac>
 715                                     <mml:mfrac>
 716                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 717                                         <mml:mi mathvariant="italic">d</mml:mi>
 718                                         </mml:msub>
 719                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 720                                         <mml:mi mathvariant="italic">A</mml:mi>
 721                                         </mml:msub>
 722                                     </mml:mfrac>
 723                                     <mml:mfrac>
 724                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 725                                         <mml:mi mathvariant="italic">d</mml:mi>
 726                                         </mml:msub>
 727                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 728                                         <mml:mi mathvariant="italic">A</mml:mi>
 729                                         </mml:msub>
 730                                     </mml:mfrac>
 731                                     <mml:mfrac>
 732                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 733                                         <mml:mi mathvariant="italic">d</mml:mi>
 734                                         </mml:msub>
 735                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 736                                         <mml:mi mathvariant="italic">A</mml:mi>
 737                                         </mml:msub>
 738                                     </mml:mfrac>
 739                                 </mml:mfenced>
 740                             </mml:mrow>
 741                         </mml:math></inlineequation>
 742                         </entry>
 743                     </row>
 744                     <row>
 745                         <entry align="left">
 746                         <constant>GL_CONSTANT_COLOR</constant>
 747                         </entry>
 748                         <entry align="left">
 749                         <inlineequation><mml:math>
 750                             <!-- eqn: ( R sub c, G sub c, B sub c, A sub c ):-->
 751                             <mml:mfenced open="(" close=")">
 752                                 <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 753                                 <mml:mi mathvariant="italic">c</mml:mi>
 754                                 </mml:msub>
 755                                 <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 756                                 <mml:mi mathvariant="italic">c</mml:mi>
 757                                 </mml:msub>
 758                                 <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 759                                 <mml:mi mathvariant="italic">c</mml:mi>
 760                                 </mml:msub>
 761                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 762                                 <mml:mi mathvariant="italic">c</mml:mi>
 763                                 </mml:msub>
 764                             </mml:mfenced>
 765                         </mml:math></inlineequation>
 766                         </entry>
 767                     </row>
 768                     <row>
 769                         <entry align="left">
 770                         <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>
 771                         </entry>
 772                         <entry align="left">
 773                         <inlineequation><mml:math>
 774                             <!-- eqn: ( 1,  1,  1,  1 )  -  ( R sub c, G sub c, B sub c, A sub c ):-->
 775                             <mml:mrow>
 776                                 <mml:mfenced open="(" close=")">
 777                                     <mml:mn>1</mml:mn>
 778                                     <mml:mn>1</mml:mn>
 779                                     <mml:mn>1</mml:mn>
 780                                     <mml:mn>1</mml:mn>
 781                                 </mml:mfenced>
 782                                 <mml:mo>-</mml:mo>
 783                                 <mml:mfenced open="(" close=")">
 784                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 785                                     <mml:mi mathvariant="italic">c</mml:mi>
 786                                     </mml:msub>
 787                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 788                                     <mml:mi mathvariant="italic">c</mml:mi>
 789                                     </mml:msub>
 790                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 791                                     <mml:mi mathvariant="italic">c</mml:mi>
 792                                     </mml:msub>
 793                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 794                                     <mml:mi mathvariant="italic">c</mml:mi>
 795                                     </mml:msub>
 796                                 </mml:mfenced>
 797                             </mml:mrow>
 798                         </mml:math></inlineequation>
 799                         </entry>
 800                     </row>
 801                     <row>
 802                         <entry align="left">
 803                         <constant>GL_CONSTANT_ALPHA</constant>
 804                         </entry>
 805                         <entry align="left">
 806                         <inlineequation><mml:math>
 807                             <!-- eqn: ( A sub c, A sub c, A sub c, A sub c ):-->
 808                             <mml:mfenced open="(" close=")">
 809                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 810                                 <mml:mi mathvariant="italic">c</mml:mi>
 811                                 </mml:msub>
 812                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 813                                 <mml:mi mathvariant="italic">c</mml:mi>
 814                                 </mml:msub>
 815                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 816                                 <mml:mi mathvariant="italic">c</mml:mi>
 817                                 </mml:msub>
 818                                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 819                                 <mml:mi mathvariant="italic">c</mml:mi>
 820                                 </mml:msub>
 821                             </mml:mfenced>
 822                         </mml:math></inlineequation>
 823                         </entry>
 824                     </row>
 825                     <row>
 826                         <entry align="left">
 827                         <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant>
 828                         </entry>
 829                         <entry align="left">
 830                         <inlineequation><mml:math>
 831                             <!-- eqn: ( 1,  1,  1,  1 )  -  ( A sub c, A sub c, A sub c, A sub c ):-->
 832                             <mml:mrow>
 833                                 <mml:mfenced open="(" close=")">
 834                                     <mml:mn>1</mml:mn>
 835                                     <mml:mn>1</mml:mn>
 836                                     <mml:mn>1</mml:mn>
 837                                     <mml:mn>1</mml:mn>
 838                                 </mml:mfenced>
 839                                 <mml:mo>-</mml:mo>
 840                                 <mml:mfenced open="(" close=")">
 841                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 842                                     <mml:mi mathvariant="italic">c</mml:mi>
 843                                     </mml:msub>
 844                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 845                                     <mml:mi mathvariant="italic">c</mml:mi>
 846                                     </mml:msub>
 847                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 848                                     <mml:mi mathvariant="italic">c</mml:mi>
 849                                     </mml:msub>
 850                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 851                                     <mml:mi mathvariant="italic">c</mml:mi>
 852                                     </mml:msub>
 853                                 </mml:mfenced>
 854                             </mml:mrow>
 855                         </mml:math></inlineequation>
 856                         </entry>
 857                     </row>
 858                     <row>
 859                         <entry align="left">
 860                         <constant>GL_SRC_ALPHA_SATURATE</constant>
 861                         </entry>
 862                         <entry align="left">
 863                         <inlineequation><mml:math>
 864                             <!-- eqn: ( i,  i,  i,  1 ):-->
 865                             <mml:mfenced open="(" close=")">
 866                                 <mml:mi mathvariant="italic">i</mml:mi>
 867                                 <mml:mi mathvariant="italic">i</mml:mi>
 868                                 <mml:mi mathvariant="italic">i</mml:mi>
 869                                 <mml:mn>1</mml:mn>
 870                             </mml:mfenced>
 871                         </mml:math></inlineequation>
 872                         </entry>
 873                     </row>
 874                 </tbody>
 875             </tgroup>
 876         </informaltable>
 877         <para>
 878             In the table,
 879         </para>
 880         <para>
 881             <para>
 882                 <inlineequation><mml:math>
 883                     <!-- eqn: i  =   min (A sub s ,  k sub A  -  A sub d )  /  k sub A:-->
 884                     <mml:mrow>
 885                         <mml:mi mathvariant="italic">i</mml:mi>
 886                         <mml:mo>=</mml:mo>
 887                         <mml:mfrac>
 888                             <mml:mrow>
 889                                 <mml:mi mathvariant="italic">min</mml:mi>
 890                                 <mml:mo>&af;</mml:mo>
 891                                 <mml:mfenced open="(" close=")">
 892                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 893                                     <mml:mi mathvariant="italic">s</mml:mi>
 894                                     </mml:msub>
 895                                     <mml:mrow>
 896                                         <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 897                                         <mml:mi mathvariant="italic">A</mml:mi>
 898                                         </mml:msub>
 899                                         <mml:mo>-</mml:mo>
 900                                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
 901                                         <mml:mi mathvariant="italic">d</mml:mi>
 902                                         </mml:msub>
 903                                     </mml:mrow>
 904                                 </mml:mfenced>
 905                             </mml:mrow>
 906                             <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 907                             <mml:mi mathvariant="italic">A</mml:mi>
 908                             </mml:msub>
 909                         </mml:mfrac>
 910                     </mml:mrow>
 911                 </mml:math></inlineequation>
 912             </para>
 913         </para>
 914         <para>
 915             To determine the blended RGBA values of a pixel when drawing in RGBA mode,
 916             the system uses the following equations:
 917         </para>
 918         <para>
 919             <para>
 920                 <inlineequation><mml:math>
 921                     <!-- eqn: R sub d  =      min ( k sub R,  R sub s s sub R + R sub d d sub R ):-->
 922                     <mml:mrow>
 923                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 924                         <mml:mi mathvariant="italic">d</mml:mi>
 925                         </mml:msub>
 926                         <mml:mo>=</mml:mo>
 927                         <mml:mrow>
 928                             <mml:mi mathvariant="italic">min</mml:mi>
 929                             <mml:mo>&af;</mml:mo>
 930                             <mml:mfenced open="(" close=")">
 931                                 <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 932                                 <mml:mi mathvariant="italic">R</mml:mi>
 933                                 </mml:msub>
 934                                 <mml:mrow>
 935                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 936                                     <mml:mi mathvariant="italic">s</mml:mi>
 937                                     </mml:msub>
 938                                     <mml:mo>&it;</mml:mo>
 939                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 940                                     <mml:mi mathvariant="italic">R</mml:mi>
 941                                     </mml:msub>
 942                                     <mml:mo>+</mml:mo>
 943                                     <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
 944                                     <mml:mi mathvariant="italic">d</mml:mi>
 945                                     </mml:msub>
 946                                     <mml:mo>&it;</mml:mo>
 947                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 948                                     <mml:mi mathvariant="italic">R</mml:mi>
 949                                     </mml:msub>
 950                                 </mml:mrow>
 951                             </mml:mfenced>
 952                         </mml:mrow>
 953                     </mml:mrow>
 954                 </mml:math></inlineequation>
 955                 <inlineequation><mml:math>
 956                     <!-- eqn: G sub d  =    min ( k sub G,  G sub s s sub G + G sub d d sub G ):-->
 957                     <mml:mrow>
 958                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 959                         <mml:mi mathvariant="italic">d</mml:mi>
 960                         </mml:msub>
 961                         <mml:mo>=</mml:mo>
 962                         <mml:mrow>
 963                             <mml:mi mathvariant="italic">min</mml:mi>
 964                             <mml:mo>&af;</mml:mo>
 965                             <mml:mfenced open="(" close=")">
 966                                 <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
 967                                 <mml:mi mathvariant="italic">G</mml:mi>
 968                                 </mml:msub>
 969                                 <mml:mrow>
 970                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 971                                     <mml:mi mathvariant="italic">s</mml:mi>
 972                                     </mml:msub>
 973                                     <mml:mo>&it;</mml:mo>
 974                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
 975                                     <mml:mi mathvariant="italic">G</mml:mi>
 976                                     </mml:msub>
 977                                     <mml:mo>+</mml:mo>
 978                                     <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
 979                                     <mml:mi mathvariant="italic">d</mml:mi>
 980                                     </mml:msub>
 981                                     <mml:mo>&it;</mml:mo>
 982                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
 983                                     <mml:mi mathvariant="italic">G</mml:mi>
 984                                     </mml:msub>
 985                                 </mml:mrow>
 986                             </mml:mfenced>
 987                         </mml:mrow>
 988                     </mml:mrow>
 989                 </mml:math></inlineequation>
 990                 <inlineequation><mml:math>
 991                     <!-- eqn: B sub d  =    min ( k sub B,  B sub s s sub B + B sub d d sub B ):-->
 992                     <mml:mrow>
 993                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
 994                         <mml:mi mathvariant="italic">d</mml:mi>
 995                         </mml:msub>
 996                         <mml:mo>=</mml:mo>
 997                         <mml:mrow>
 998                             <mml:mi mathvariant="italic">min</mml:mi>
 999                             <mml:mo>&af;</mml:mo>
1000                             <mml:mfenced open="(" close=")">
1001                                 <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
1002                                 <mml:mi mathvariant="italic">B</mml:mi>
1003                                 </mml:msub>
1004                                 <mml:mrow>
1005                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
1006                                     <mml:mi mathvariant="italic">s</mml:mi>
1007                                     </mml:msub>
1008                                     <mml:mo>&it;</mml:mo>
1009                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
1010                                     <mml:mi mathvariant="italic">B</mml:mi>
1011                                     </mml:msub>
1012                                     <mml:mo>+</mml:mo>
1013                                     <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
1014                                     <mml:mi mathvariant="italic">d</mml:mi>
1015                                     </mml:msub>
1016                                     <mml:mo>&it;</mml:mo>
1017                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
1018                                     <mml:mi mathvariant="italic">B</mml:mi>
1019                                     </mml:msub>
1020                                 </mml:mrow>
1021                             </mml:mfenced>
1022                         </mml:mrow>
1023                     </mml:mrow>
1024                 </mml:math></inlineequation>
1025                 <inlineequation><mml:math>
1026                     <!-- eqn: A sub d  =    min ( k sub A,  A sub s s sub A + A sub d d sub A ):-->
1027                     <mml:mrow>
1028                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1029                         <mml:mi mathvariant="italic">d</mml:mi>
1030                         </mml:msub>
1031                         <mml:mo>=</mml:mo>
1032                         <mml:mrow>
1033                             <mml:mi mathvariant="italic">min</mml:mi>
1034                             <mml:mo>&af;</mml:mo>
1035                             <mml:mfenced open="(" close=")">
1036                                 <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
1037                                 <mml:mi mathvariant="italic">A</mml:mi>
1038                                 </mml:msub>
1039                                 <mml:mrow>
1040                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1041                                     <mml:mi mathvariant="italic">s</mml:mi>
1042                                     </mml:msub>
1043                                     <mml:mo>&it;</mml:mo>
1044                                     <mml:msub><mml:mi mathvariant="italic">s</mml:mi>
1045                                     <mml:mi mathvariant="italic">A</mml:mi>
1046                                     </mml:msub>
1047                                     <mml:mo>+</mml:mo>
1048                                     <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1049                                     <mml:mi mathvariant="italic">d</mml:mi>
1050                                     </mml:msub>
1051                                     <mml:mo>&it;</mml:mo>
1052                                     <mml:msub><mml:mi mathvariant="italic">d</mml:mi>
1053                                     <mml:mi mathvariant="italic">A</mml:mi>
1054                                     </mml:msub>
1055                                 </mml:mrow>
1056                             </mml:mfenced>
1057                         </mml:mrow>
1058                     </mml:mrow>
1059                 </mml:math></inlineequation>
1060             </para>
1061         </para>
1062         <para>
1063             Despite the apparent precision of the above equations,
1064             blending arithmetic is not exactly specified,
1065             because blending operates with imprecise integer color values.
1066             However,
1067             a blend factor that should be equal to 1
1068             is guaranteed not to modify its multiplicand,
1069             and a blend factor equal to 0 reduces its multiplicand to 0.
1070             For example,
1071             when <parameter>sfactor</parameter> is <constant>GL_SRC_ALPHA</constant>,
1072             <parameter>dfactor</parameter> is <constant>GL_ONE_MINUS_SRC_ALPHA</constant>,
1073             and
1074             <inlineequation><mml:math>
1075                 <!-- eqn: A sub s:-->
1076                 <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1077                 <mml:mi mathvariant="italic">s</mml:mi>
1078                 </mml:msub>
1079             </mml:math></inlineequation>
1080             is equal to
1081             <inlineequation><mml:math>
1082                 <!-- eqn: k sub A:-->
1083                 <mml:msub><mml:mi mathvariant="italic">k</mml:mi>
1084                 <mml:mi mathvariant="italic">A</mml:mi>
1085                 </mml:msub>
1086             </mml:math></inlineequation>,
1087             the equations reduce to simple replacement:
1088         </para>
1089         <para>
1090             <para>
1091                 <inlineequation><mml:math>
1092                     <!-- eqn: R sub d  =      R sub s:-->
1093                     <mml:mrow>
1094                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
1095                         <mml:mi mathvariant="italic">d</mml:mi>
1096                         </mml:msub>
1097                         <mml:mo>=</mml:mo>
1098                         <mml:msub><mml:mi mathvariant="italic">R</mml:mi>
1099                         <mml:mi mathvariant="italic">s</mml:mi>
1100                         </mml:msub>
1101                     </mml:mrow>
1102                 </mml:math></inlineequation>
1103                 <inlineequation><mml:math>
1104                     <!-- eqn: G sub d  =    G sub s:-->
1105                     <mml:mrow>
1106                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
1107                         <mml:mi mathvariant="italic">d</mml:mi>
1108                         </mml:msub>
1109                         <mml:mo>=</mml:mo>
1110                         <mml:msub><mml:mi mathvariant="italic">G</mml:mi>
1111                         <mml:mi mathvariant="italic">s</mml:mi>
1112                         </mml:msub>
1113                     </mml:mrow>
1114                 </mml:math></inlineequation>
1115                 <inlineequation><mml:math>
1116                     <!-- eqn: B sub d  =    B sub s:-->
1117                     <mml:mrow>
1118                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
1119                         <mml:mi mathvariant="italic">d</mml:mi>
1120                         </mml:msub>
1121                         <mml:mo>=</mml:mo>
1122                         <mml:msub><mml:mi mathvariant="italic">B</mml:mi>
1123                         <mml:mi mathvariant="italic">s</mml:mi>
1124                         </mml:msub>
1125                     </mml:mrow>
1126                 </mml:math></inlineequation>
1127                 <inlineequation><mml:math>
1128                     <!-- eqn: A sub d  =    A sub s:-->
1129                     <mml:mrow>
1130                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1131                         <mml:mi mathvariant="italic">d</mml:mi>
1132                         </mml:msub>
1133                         <mml:mo>=</mml:mo>
1134                         <mml:msub><mml:mi mathvariant="italic">A</mml:mi>
1135                         <mml:mi mathvariant="italic">s</mml:mi>
1136                         </mml:msub>
1137                     </mml:mrow>
1138                 </mml:math></inlineequation>
1139             </para>
1140         </para>
1141         <para>
1142         </para>
1143     </refsect1>
1144     <refsect1 id="examples"><title>Examples</title>
1145         <para>
1146         </para>
1147         <para>
1148             Transparency is best implemented using blend function
1149             (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>)
1150             with primitives sorted from farthest to nearest.
1151             Note that this transparency calculation does not require
1152             the presence of alpha bitplanes in the frame buffer.
1153         </para>
1154         <para>
1155             Blend function
1156             (<constant>GL_SRC_ALPHA</constant>, <constant>GL_ONE_MINUS_SRC_ALPHA</constant>)
1157             is also useful for rendering antialiased points and lines
1158             in arbitrary order.
1159         </para>
1160         <para>
1161             Polygon antialiasing is optimized using blend function
1162             (<constant>GL_SRC_ALPHA_SATURATE</constant>, <constant>GL_ONE</constant>)
1163             with polygons sorted from nearest to farthest.
1164             (See the <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry> reference page and the
1165             <constant>GL_POLYGON_SMOOTH</constant> argument for information on polygon antialiasing.)
1166             Destination alpha bitplanes,
1167             which must be present for this blend function to operate correctly,
1168             store the accumulated coverage.
1169         </para>
1170     </refsect1>
1171     <refsect1 id="notes"><title>Notes</title>
1172         <para>
1173             Incoming (source) alpha is correctly thought of as a material opacity,
1174             ranging from 1.0
1175             (<inlineequation><mml:math>
1176                 <!-- eqn: K sub A:-->
1177                 <mml:msub><mml:mi mathvariant="italic">K</mml:mi>
1178                 <mml:mi mathvariant="italic">A</mml:mi>
1179                 </mml:msub>
1180             </mml:math></inlineequation>),
1181             representing complete opacity,
1182             to 0.0 (0), representing complete
1183             transparency.
1184         </para>
1185         <para>
1186             When more than one color buffer is enabled for drawing,
1187             the GL performs blending separately for each enabled buffer,
1188             using the contents of that buffer for destination color.
1189             (See <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>.)
1190         </para>
1191         <para>
1192             Blending affects only RGBA rendering.
1193             It is ignored by color index renderers.
1194         </para>
1195         <para>
1196             <constant>GL_CONSTANT_COLOR</constant>, <constant>GL_ONE_MINUS_CONSTANT_COLOR</constant>,
1197             <constant>GL_CONSTANT_ALPHA</constant>, <constant>GL_ONE_MINUS_CONSTANT_ALPHA</constant> are available only
1198             if the GL version is 1.4 or greater or if the <code>ARB_imaging</code> is
1199             supported by your implementation.
1200         </para>
1201         <para>
1202             <constant>GL_SRC_COLOR</constant> and <constant>GL_ONE_MINUS_SRC_COLOR</constant> are valid only for
1203             <parameter>sfactor</parameter> if the GL version is 1.4 or greater.
1204         </para>
1205         <para>
1206             <constant>GL_DST_COLOR</constant> and <constant>GL_ONE_MINUS_DST_COLOR</constant> are valid only for
1207             <parameter>dfactor</parameter> if the GL version is 1.4 or greater.
1208         </para>
1209     </refsect1>
1210     <refsect1 id="errors"><title>Errors</title>
1211         <para>
1212             <constant>GL_INVALID_ENUM</constant> is generated if either <parameter>sfactor</parameter> or <parameter>dfactor</parameter> is not an
1213             accepted value.
1214         </para>
1215         <para>
1216             <constant>GL_INVALID_OPERATION</constant> is generated if <function>glBlendFunc</function>
1217             is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
1218             and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
1219         </para>
1220     </refsect1>
1221     <refsect1 id="associatedgets"><title>Associated Gets</title>
1222         <para>
1223             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_SRC</constant>
1224         </para>
1225         <para>
1226             <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_BLEND_DST</constant>
1227         </para>
1228         <para>
1229             <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_BLEND</constant>
1230         </para>
1231         <para>
1232         </para>
1233     </refsect1>
1234     <refsect1 id="seealso"><title>See Also</title>
1235         <para>
1236             <citerefentry><refentrytitle>glAlphaFunc</refentrytitle></citerefentry>,
1237             <citerefentry><refentrytitle>glBlendColor</refentrytitle></citerefentry>,
1238             <citerefentry><refentrytitle>glBlendEquation</refentrytitle></citerefentry>,
1239             <citerefentry><refentrytitle>glBlendFuncSeparate</refentrytitle></citerefentry>,
1240             <citerefentry><refentrytitle>glClear</refentrytitle></citerefentry>,
1241             <citerefentry><refentrytitle>glDrawBuffer</refentrytitle></citerefentry>,
1242             <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
1243             <citerefentry><refentrytitle>glLogicOp</refentrytitle></citerefentry>,
1244             <citerefentry><refentrytitle>glStencilFunc</refentrytitle></citerefentry>
1245
1246         </para>
1247     </refsect1>
1248     <refsect1 id="Copyright"><title>Copyright</title>
1249         <para>
1250             Copyright <trademark class="copyright"></trademark> 1991-2006
1251             Silicon Graphics, Inc. This document is licensed under the SGI
1252             Free Software B License. For details, see
1253             <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
1254         </para>
1255     </refsect1>
1256 </refentry>