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1 | <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "xhtml1-transitional.dtd"> |
2 | <!-- saved from url=(0013)about:internet --> | |
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> |