upstream-man-pages/man2/xhtml/glEvalPoint.xml

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   3 <?xml-stylesheet type="text/xsl" href="mathml.xsl"?><html xmlns="http://www.w3.org/1999/xhtml" xmlns:pref="http://www.w3.org/2002/Math/preference" pref:renderer="mathplayer-dl"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>glEvalPoint</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glEvalPoint"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glEvalPoint — generate and evaluate a single point in a mesh</p></div><div class="refsynopsisdiv"><h2>C Specification</h2><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalPoint1</b>(</code></td><td>GLint  </td><td><var class="pdparam">i</var><code>)</code>;</td></tr></table></div><div class="funcsynopsis"><table border="0" summary="Function synopsis" cellspacing="0" cellpadding="0"><tr><td><code class="funcdef">void <b class="fsfunc">glEvalPoint2</b>(</code></td><td>GLint  </td><td><var class="pdparam">i</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">j</var><code>)</code>;</td></tr></table></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><em class="parameter"><code>i</code></em></span></dt><dd><p>
   4                     Specifies the integer value for grid domain variable
   5                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">i</mml:mi></mml:math>.
   6                 </p></dd><dt><span class="term"><em class="parameter"><code>j</code></em></span></dt><dd><p>
   7                     Specifies the integer value for grid domain variable
   8                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">j</mml:mi></mml:math>
   9                     (<code class="function">glEvalPoint2</code> only).
  10                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  11             <a class="citerefentry" href="glMapGrid.xml"><span class="citerefentry"><span class="refentrytitle">glMapGrid</span></span></a> and <a class="citerefentry" href="glEvalMesh.xml"><span class="citerefentry"><span class="refentrytitle">glEvalMesh</span></span></a> are used in tandem to efficiently
  12             generate and evaluate a series of evenly spaced map domain values.
  13             <code class="function">glEvalPoint</code> can be used to evaluate a single grid point in the same gridspace
  14             that is traversed by <a class="citerefentry" href="glEvalMesh.xml"><span class="citerefentry"><span class="refentrytitle">glEvalMesh</span></span></a>.
  15             Calling <code class="function">glEvalPoint1</code> is equivalent to calling
  16             </p><pre class="programlisting">
  17 glEvalCoord1( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  18
  19                   <mml:mrow>
  20                       <mml:mrow>
  21                           <mml:mn>i</mml:mn>
  22                           <mml:mo>·</mml:mo>
  23                           <mml:mo>Δ</mml:mo>
  24                           <mml:mi mathvariant="italic">u</mml:mi>
  25                       </mml:mrow>
  26                       <mml:mo>+</mml:mo>
  27                       <mml:msub>
  28                           <mml:mi mathvariant="italic">u</mml:mi>
  29                           <mml:mn>1</mml:mn>
  30                       </mml:msub>
  31                   </mml:mrow>
  32               </mml:math> );
  33          </pre><p>
  34             where
  35             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  36
  37                 <mml:mrow>
  38                     <mml:mrow>
  39                         <mml:mo>Δ</mml:mo>
  40                         <mml:mi mathvariant="italic">u</mml:mi>
  41                     </mml:mrow>
  42                     <mml:mo>=</mml:mo>
  43                     <mml:mfrac>
  44                         <mml:mfenced open="(" close=")">
  45                             <mml:mrow>
  46                                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
  47                                 <mml:mn>2</mml:mn>
  48                                 </mml:msub>
  49                                 <mml:mo>-</mml:mo>
  50                                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
  51                                 <mml:mn>1</mml:mn>
  52                                 </mml:msub>
  53                             </mml:mrow>
  54                         </mml:mfenced>
  55                         <mml:mi mathvariant="italic">n</mml:mi>
  56                     </mml:mfrac>
  57                 </mml:mrow>
  58             </mml:math></div><p>
  59         </p><p>
  60             and
  61             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>,
  62             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  63
  64                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
  65                 <mml:mn>1</mml:mn>
  66                 </mml:msub>
  67             </mml:math>,
  68             and
  69             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  70
  71                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
  72                 <mml:mn>2</mml:mn>
  73                 </mml:msub>
  74             </mml:math>
  75             are the arguments to the most recent <a class="citerefentry" href="glMapGrid1.xml"><span class="citerefentry"><span class="refentrytitle">glMapGrid1</span></span></a> command.
  76             The one absolute numeric requirement is that if
  77             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  78
  79                 <mml:mrow>
  80                     <mml:mi mathvariant="italic">i</mml:mi>
  81                     <mml:mo>=</mml:mo>
  82                     <mml:mi mathvariant="italic">n</mml:mi>
  83                 </mml:mrow>
  84             </mml:math>,
  85             then the value computed from
  86             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
  87
  88                 <mml:mrow>
  89                     <mml:mrow>
  90                         <mml:mi mathvariant="italic">i</mml:mi>
  91                         <mml:mo>·</mml:mo>
  92                         <mml:mrow>
  93                             <mml:mo>Δ</mml:mo>
  94                             <mml:mi mathvariant="italic">u</mml:mi>
  95                         </mml:mrow>
  96                     </mml:mrow>
  97                     <mml:mo>+</mml:mo>
  98                     <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
  99                     <mml:mn>1</mml:mn>
 100                     </mml:msub>
 101                 </mml:mrow>
 102             </mml:math>
 103             is exactly
 104             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 105
 106                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 107                 <mml:mn>2</mml:mn>
 108                 </mml:msub>
 109             </mml:math>.
 110         </p><p>
 111             In the two-dimensional case, <code class="function">glEvalPoint2</code>, let
 112         </p><p>
 113             </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 114
 115                 <mml:mrow>
 116                     <mml:mrow>
 117                         <mml:mo>Δ</mml:mo>
 118                         <mml:mi mathvariant="italic">u</mml:mi>
 119                     </mml:mrow>
 120                     <mml:mo>=</mml:mo>
 121                     <mml:mfrac>
 122                         <mml:mfenced open="(" close=")">
 123                             <mml:mrow>
 124                                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 125                                 <mml:mn>2</mml:mn>
 126                                 </mml:msub>
 127                                 <mml:mo>-</mml:mo>
 128                                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 129                                 <mml:mn>1</mml:mn>
 130                                 </mml:msub>
 131                             </mml:mrow>
 132                         </mml:mfenced>
 133                         <mml:mi mathvariant="italic">n</mml:mi>
 134                     </mml:mfrac>
 135                 </mml:mrow>
 136             </mml:math></div><p>
 137             </p><p>
 138                 </p><div class="informalequation"><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 139
 140                     <mml:mrow>
 141                         <mml:mrow>
 142                             <mml:mo>Δ</mml:mo>
 143                             <mml:mi mathvariant="italic">v</mml:mi>
 144                         </mml:mrow>
 145                         <mml:mo>=</mml:mo>
 146                         <mml:mfrac>
 147                             <mml:mfenced open="(" close=")">
 148                                 <mml:mrow>
 149                                     <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 150                                     <mml:mn>2</mml:mn>
 151                                     </mml:msub>
 152                                     <mml:mo>-</mml:mo>
 153                                     <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 154                                     <mml:mn>1</mml:mn>
 155                                     </mml:msub>
 156                                 </mml:mrow>
 157                             </mml:mfenced>
 158                             <mml:mi mathvariant="italic">m</mml:mi>
 159                         </mml:mfrac>
 160                     </mml:mrow>
 161                 </mml:math></div><p>
 162             </p><p>
 163         </p><p>
 164             where
 165             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>,
 166             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 167
 168                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 169                 <mml:mn>1</mml:mn>
 170                 </mml:msub>
 171             </mml:math>,
 172             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 173
 174                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 175                 <mml:mn>2</mml:mn>
 176                 </mml:msub>
 177             </mml:math>,
 178             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">m</mml:mi></mml:math>,
 179             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 180
 181                 <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 182                 <mml:mn>1</mml:mn>
 183                 </mml:msub>
 184             </mml:math>,
 185             and
 186             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 187
 188                 <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 189                 <mml:mn>2</mml:mn>
 190                 </mml:msub>
 191             </mml:math>
 192             are the arguments to the most recent <a class="citerefentry" href="glMapGrid2.xml"><span class="citerefentry"><span class="refentrytitle">glMapGrid2</span></span></a> command.
 193             Then the <code class="function">glEvalPoint2</code> command is equivalent to calling
 194             </p><pre class="programlisting">
 195 glEvalCoord2( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 196
 197                         <mml:mrow>
 198                             <mml:mrow>
 199                                 <mml:mn>i</mml:mn>
 200                                 <mml:mo>·</mml:mo>
 201                                 <mml:mo>Δ</mml:mo>
 202                                 <mml:mi mathvariant="italic">u</mml:mi>
 203                             </mml:mrow>
 204                             <mml:mo>+</mml:mo>
 205                             <mml:msub>
 206                                 <mml:mi mathvariant="italic">u</mml:mi>
 207                                 <mml:mn>1</mml:mn>
 208                             </mml:msub>
 209                             <mml:mo>,</mml:mo>
 210
 211                             <mml:mrow>
 212                                 <mml:mn>j</mml:mn>
 213                                 <mml:mo>·</mml:mo>
 214                                 <mml:mo>Δ</mml:mo>
 215                                 <mml:mi mathvariant="italic">v</mml:mi>
 216
 217                             </mml:mrow>
 218                             <mml:mo>+</mml:mo>
 219                             <mml:msub>
 220                                 <mml:mi mathvariant="italic">v</mml:mi>
 221                                 <mml:mn>1</mml:mn>
 222                             </mml:msub>
 223                         </mml:mrow>
 224                     </mml:math> );
 225             </pre><p>
 226             The only absolute numeric requirements are that if
 227             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 228
 229                 <mml:mrow>
 230                     <mml:mi mathvariant="italic">i</mml:mi>
 231                     <mml:mo>=</mml:mo>
 232                     <mml:mi mathvariant="italic">n</mml:mi>
 233                 </mml:mrow>
 234             </mml:math>,
 235             then the value computed from
 236             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 237
 238                 <mml:mrow>
 239                     <mml:mrow>
 240                         <mml:mi mathvariant="italic">i</mml:mi>
 241                         <mml:mo>·</mml:mo>
 242                         <mml:mrow>
 243                             <mml:mo>Δ</mml:mo>
 244                             <mml:mi mathvariant="italic">u</mml:mi>
 245                         </mml:mrow>
 246                     </mml:mrow>
 247                     <mml:mo>+</mml:mo>
 248                     <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 249                     <mml:mn>1</mml:mn>
 250                     </mml:msub>
 251                 </mml:mrow>
 252             </mml:math>
 253             is exactly
 254             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 255
 256                 <mml:msub><mml:mi mathvariant="italic">u</mml:mi>
 257                 <mml:mn>2</mml:mn>
 258                 </mml:msub>
 259             </mml:math>,
 260             and if
 261             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 262
 263                 <mml:mrow>
 264                     <mml:mi mathvariant="italic">j</mml:mi>
 265                     <mml:mo>=</mml:mo>
 266                     <mml:mi mathvariant="italic">m</mml:mi>
 267                 </mml:mrow>
 268             </mml:math>,
 269             then the value computed from
 270             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 271
 272                 <mml:mrow>
 273                     <mml:mrow>
 274                         <mml:mi mathvariant="italic">j</mml:mi>
 275                         <mml:mo>·</mml:mo>
 276                         <mml:mrow>
 277                             <mml:mo>Δ</mml:mo>
 278                             <mml:mi mathvariant="italic">v</mml:mi>
 279                         </mml:mrow>
 280                     </mml:mrow>
 281                     <mml:mo>+</mml:mo>
 282                     <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 283                     <mml:mn>1</mml:mn>
 284                     </mml:msub>
 285                 </mml:mrow>
 286             </mml:math>
 287             is exactly
 288             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 289
 290                 <mml:msub><mml:mi mathvariant="italic">v</mml:mi>
 291                 <mml:mn>2</mml:mn>
 292                 </mml:msub>
 293             </mml:math>.
 294         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="associatedgets"></a><h2>Associated Gets</h2><p>
 295             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAP1_GRID_DOMAIN</code>
 296         </p><p>
 297             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAP2_GRID_DOMAIN</code>
 298         </p><p>
 299             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAP1_GRID_SEGMENTS</code>
 300         </p><p>
 301             <a class="citerefentry" href="glGet.xml"><span class="citerefentry"><span class="refentrytitle">glGet</span></span></a> with argument <code class="constant">GL_MAP2_GRID_SEGMENTS</code>
 302         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 303             <a class="citerefentry" href="glEvalCoord.xml"><span class="citerefentry"><span class="refentrytitle">glEvalCoord</span></span></a>,
 304             <a class="citerefentry" href="glEvalMesh.xml"><span class="citerefentry"><span class="refentrytitle">glEvalMesh</span></span></a>,
 305             <a class="citerefentry" href="glMap1.xml"><span class="citerefentry"><span class="refentrytitle">glMap1</span></span></a>,
 306             <a class="citerefentry" href="glMap2.xml"><span class="citerefentry"><span class="refentrytitle">glMap2</span></span></a>,
 307             <a class="citerefentry" href="glMapGrid.xml"><span class="citerefentry"><span class="refentrytitle">glMapGrid</span></span></a>
 308         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 309             Copyright <span class="trademark"></span>© 1991-2006
 310             Silicon Graphics, Inc. This document is licensed under the SGI
 311             Free Software B License. For details, see
 312             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 313         </p></div></div></body></html>