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| 5 | <title>definetri.pro (SAXO Documentation Assistant)</title> |
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| 48 | <a href="completecointerre.html"><img src="./../../prev.gif" border="0" alt="Previous"></a></td> |
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| 49 | <td width="80%" align="center" valign="center"> |
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| 50 | <font size=-1><i>SAXO Documentation Assistant</i>: <a href="./../../home.html">Overview</a></font></td> |
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| 51 | <td width="10%" align="right"> |
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| 52 | <a href="definetri_e.html"><img src="./../../next.gif" border="0" alt="Next"></a></td> |
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| 53 | </tr> |
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| 54 | </table> |
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| 55 | |
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| 56 | |
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| 57 | <h1><font size="-2">ToBeReviewed/TRIANGULATION/</font></h1> |
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| 58 | <h2>definetri.pro</h2> |
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| 59 | |
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| 60 | <dl> |
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| 61 | </dl> |
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| 62 | |
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| 63 | |
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[290] | 64 | Define a triangulation array like <a href="/Applications/rsi/idl_6.3/help/online_help/TRIANGULATE.html">TRIANGULATE</a>. |
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[163] | 65 | But in a VERY SIMPLE CASE: |
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[321] | 66 | the points are regularly-gridded on nx*ny array. |
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[163] | 67 | Find a Delaunay triangulation for this set of points is easy: |
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[234] | 68 | Points define (nx-1)*(ny-1) rectangles which we can cut in 2 triangles. |
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[187] | 69 | cf. figure above |
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[163] | 70 | |
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[191] | 71 | <pre> |
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[187] | 72 | fixe |
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[163] | 73 | ny-1*---*---*. . . . . .*---*---* |
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[234] | 74 | | +| +| | +| +| |
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[163] | 75 | | + | + | | + | + | |
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| 76 | |+ |+ | |+ |+ | |
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[234] | 77 | ny-2*---*---*. . . . . .*---*---* |
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[163] | 78 | . . . . |
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| 79 | . . . . |
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| 80 | . . . . |
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| 81 | 1*---*---*. . . . . .*---*---* |
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| 82 | | +| +| | +| +| |
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| 83 | | + | + | | + | + | |
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| 84 | |+ |+ | |+ |+ | |
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[234] | 85 | 0*---*---*. . . . . .*---*---* |
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[163] | 86 | 0 1 2 nx-3 nx-2 nx-1 |
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| 87 | </pre> |
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| 88 | |
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| 89 | You have 2 ways to cut a rectangle: |
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| 90 | 1) the upward diagonal 2) the downward diagonal |
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| 91 | |
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[191] | 92 | <pre> |
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[163] | 93 | *---* *---* |
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| 94 | | +| |+ | |
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| 95 | | + | | + | |
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| 96 | |+ | | +| |
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[234] | 97 | *---* *---* |
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[163] | 98 | </pre> |
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| 99 | |
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| 100 | |
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| 101 | |
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| 102 | |
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| 103 | |
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| 104 | <a name="#_definetri"></a> |
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| 105 | |
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| 106 | <h2>definetri <font size="-1" color="#006633"> |
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| 107 | Utilities |
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[234] | 108 | </font></h2> |
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[163] | 109 | |
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| 110 | <p><font face="Courier"><i>result = </i>definetri(<i><a href="#_definetri_keyword_nx">nx</a>, <a href="#_definetri_keyword_ny">ny</a>[, <a href="#_definetri_keyword_downward">downward</a>]</i>)</font></p> |
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| 111 | |
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| 112 | |
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| 113 | |
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| 114 | |
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| 115 | <h3>Return value</h3> |
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[187] | 116 | triangles is a 2d array and its dimensions are 3 and 2*(nx-1)*(ny-1). |
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| 117 | triangles is defined like in the TRIANGULATE procedure. |
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[163] | 118 | |
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| 119 | |
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| 120 | |
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| 121 | <h3>Parameters</h3> |
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| 122 | |
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| 123 | |
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| 124 | <a name="#_definetri_keyword_nx"></a> |
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| 125 | <h4>nx |
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| 126 | <font size="-1" color="#006633">in</font> |
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| 127 | |
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| 128 | |
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| 129 | <font size="-1" color="#006633">required</font> |
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| 130 | |
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| 131 | |
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| 132 | |
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| 133 | |
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| 134 | </h4> |
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| 135 | |
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| 136 | |
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| 137 | The x dimension array |
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| 138 | |
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| 139 | |
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| 140 | |
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| 141 | <a name="#_definetri_keyword_ny"></a> |
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| 142 | <h4>ny |
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| 143 | <font size="-1" color="#006633">in</font> |
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| 144 | |
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| 145 | |
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| 146 | <font size="-1" color="#006633">required</font> |
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| 147 | |
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| 148 | |
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| 149 | |
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| 150 | |
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| 151 | </h4> |
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| 152 | |
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| 153 | |
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| 154 | The y dimension array |
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| 155 | |
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| 156 | |
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| 157 | |
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| 158 | <a name="#_definetri_keyword_downward"></a> |
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| 159 | <h4>downward |
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| 160 | <font size="-1" color="#006633">in</font> |
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| 161 | |
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| 162 | <font size="-1" color="#006633">optional</font> |
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| 163 | |
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| 164 | |
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| 165 | |
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| 166 | |
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| 167 | |
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| 168 | </h4> |
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| 169 | |
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| 170 | |
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[234] | 171 | When DOWNWARD is undefined all rectangles are cut in using the upward |
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| 172 | diagonal. |
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| 173 | DOWNWARD is a vector which contains the rectangles numbers which are cut in |
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[187] | 174 | using the downward diagonal. |
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[234] | 175 | The rectangle number is defined by the index (in a nx*ny vector) of the |
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[187] | 176 | lower-left corner of the rectangle. |
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[163] | 177 | |
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[234] | 183 | <h3>Examples</h3><pre> |
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[163] | 184 | |
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[187] | 185 | IDL> triangles=definetri(3,3,[1,3]) |
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| 186 | triangles will be this kind of triangulation: |
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[163] | 187 | |
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| 188 | *---*---* |
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[187] | 189 | |+ | +| |
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| 190 | | + | + | |
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| 191 | | +|+ | |
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[163] | 192 | *---*---* |
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[187] | 193 | | +|+ | |
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| 194 | | + | + | |
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| 195 | |+ | +| |
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[163] | 196 | *---*---* |
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| 197 | |
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| 198 | |
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[234] | 199 | </pre><h3>Version history</h3> |
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[163] | 200 | |
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| 201 | <h4>Version</h4> |
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[321] | 202 | $Id: definetri.pro 297 2007-09-25 15:09:12Z pinsard $ |
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[163] | 203 | <h4>History</h4> |
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| 204 | sebastien Masson (smlod@ipsl.jussieu.fr) |
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| 205 | 4/3/1999 |
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| 223 | <font size="-3"><p> </p></font> |
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| 224 | <hr size="1" color="#CCCCCC"/> |
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[187] | 229 | <p><font color="gray" size="-3"> Produced by IDLdoc 2.0.</font></p> |
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[163] | 230 | |
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| 231 | </body> |
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[249] | 232 | </html> |
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