| 1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> |
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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> |