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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="glEvalPoint"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glEvalPoint</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glEvalPoint</refname> | |
17 | <refpurpose>generate and evaluate a single point in a mesh</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glEvalPoint1</function></funcdef> | |
23 | <paramdef>GLint <parameter>i</parameter></paramdef> | |
24 | </funcprototype> | |
25 | </funcsynopsis> | |
26 | <funcsynopsis> | |
27 | <funcprototype> | |
28 | <funcdef>void <function>glEvalPoint2</function></funcdef> | |
29 | <paramdef>GLint <parameter>i</parameter></paramdef> | |
30 | <paramdef>GLint <parameter>j</parameter></paramdef> | |
31 | </funcprototype> | |
32 | </funcsynopsis> | |
33 | </refsynopsisdiv> | |
34 | <!-- eqn: ignoring delim $$ --> | |
35 | <refsect1 id="parameters"><title>Parameters</title> | |
36 | <variablelist> | |
37 | <varlistentry> | |
38 | <term><parameter>i</parameter></term> | |
39 | <listitem> | |
40 | <para> | |
41 | Specifies the integer value for grid domain variable | |
42 | <inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>. | |
43 | </para> | |
44 | </listitem> | |
45 | </varlistentry> | |
46 | <varlistentry> | |
47 | <term><parameter>j</parameter></term> | |
48 | <listitem> | |
49 | <para> | |
50 | Specifies the integer value for grid domain variable | |
51 | <inlineequation><mml:math><mml:mi mathvariant="italic">j</mml:mi></mml:math></inlineequation> | |
52 | (<function>glEvalPoint2</function> only). | |
53 | </para> | |
54 | </listitem> | |
55 | </varlistentry> | |
56 | </variablelist> | |
57 | </refsect1> | |
58 | <refsect1 id="description"><title>Description</title> | |
59 | <para> | |
60 | <citerefentry><refentrytitle>glMapGrid</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry> are used in tandem to efficiently | |
61 | generate and evaluate a series of evenly spaced map domain values. | |
62 | <function>glEvalPoint</function> can be used to evaluate a single grid point in the same gridspace | |
63 | that is traversed by <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>. | |
64 | Calling <function>glEvalPoint1</function> is equivalent to calling | |
65 | <programlisting> | |
66 | glEvalCoord1( <mml:math> | |
67 | <!-- eqn: i \cdot DELTA u + u sub 1 :--> | |
68 | <mml:mrow> | |
69 | <mml:mrow> | |
70 | <mml:mn>i</mml:mn> | |
71 | <mml:mo>·</mml:mo> | |
72 | <mml:mo>Δ</mml:mo> | |
73 | <mml:mi mathvariant="italic">u</mml:mi> | |
74 | </mml:mrow> | |
75 | <mml:mo>+</mml:mo> | |
76 | <mml:msub> | |
77 | <mml:mi mathvariant="italic">u</mml:mi> | |
78 | <mml:mn>1</mml:mn> | |
79 | </mml:msub> | |
80 | </mml:mrow> | |
81 | </mml:math> ); | |
82 | </programlisting> | |
83 | where | |
84 | <informalequation><mml:math> | |
85 | <!-- eqn: DELTA u = ( u sub 2 - u sub 1 ) / n:--> | |
86 | <mml:mrow> | |
87 | <mml:mrow> | |
88 | <mml:mo>Δ</mml:mo> | |
89 | <mml:mi mathvariant="italic">u</mml:mi> | |
90 | </mml:mrow> | |
91 | <mml:mo>=</mml:mo> | |
92 | <mml:mfrac> | |
93 | <mml:mfenced open="(" close=")"> | |
94 | <mml:mrow> | |
95 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
96 | <mml:mn>2</mml:mn> | |
97 | </mml:msub> | |
98 | <mml:mo>-</mml:mo> | |
99 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
100 | <mml:mn>1</mml:mn> | |
101 | </mml:msub> | |
102 | </mml:mrow> | |
103 | </mml:mfenced> | |
104 | <mml:mi mathvariant="italic">n</mml:mi> | |
105 | </mml:mfrac> | |
106 | </mml:mrow> | |
107 | </mml:math></informalequation> | |
108 | </para> | |
109 | <para> | |
110 | and | |
111 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>, | |
112 | <inlineequation><mml:math> | |
113 | <!-- eqn: u sub 1:--> | |
114 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
115 | <mml:mn>1</mml:mn> | |
116 | </mml:msub> | |
117 | </mml:math></inlineequation>, | |
118 | and | |
119 | <inlineequation><mml:math> | |
120 | <!-- eqn: u sub 2:--> | |
121 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
122 | <mml:mn>2</mml:mn> | |
123 | </mml:msub> | |
124 | </mml:math></inlineequation> | |
125 | are the arguments to the most recent <citerefentry><refentrytitle>glMapGrid1</refentrytitle></citerefentry> command. | |
126 | The one absolute numeric requirement is that if | |
127 | <inlineequation><mml:math> | |
128 | <!-- eqn: i = n:--> | |
129 | <mml:mrow> | |
130 | <mml:mi mathvariant="italic">i</mml:mi> | |
131 | <mml:mo>=</mml:mo> | |
132 | <mml:mi mathvariant="italic">n</mml:mi> | |
133 | </mml:mrow> | |
134 | </mml:math></inlineequation>, | |
135 | then the value computed from | |
136 | <inlineequation><mml:math> | |
137 | <!-- eqn: i cdot DELTA u + u sub 1:--> | |
138 | <mml:mrow> | |
139 | <mml:mrow> | |
140 | <mml:mi mathvariant="italic">i</mml:mi> | |
141 | <mml:mo>·</mml:mo> | |
142 | <mml:mrow> | |
143 | <mml:mo>Δ</mml:mo> | |
144 | <mml:mi mathvariant="italic">u</mml:mi> | |
145 | </mml:mrow> | |
146 | </mml:mrow> | |
147 | <mml:mo>+</mml:mo> | |
148 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
149 | <mml:mn>1</mml:mn> | |
150 | </mml:msub> | |
151 | </mml:mrow> | |
152 | </mml:math></inlineequation> | |
153 | is exactly | |
154 | <inlineequation><mml:math> | |
155 | <!-- eqn: u sub 2:--> | |
156 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
157 | <mml:mn>2</mml:mn> | |
158 | </mml:msub> | |
159 | </mml:math></inlineequation>. | |
160 | </para> | |
161 | <para> | |
162 | In the two-dimensional case, <function>glEvalPoint2</function>, let | |
163 | </para> | |
164 | <para> | |
165 | <informalequation><mml:math> | |
166 | <!-- eqn: DELTA u = ( u sub 2 - u sub 1 ) / n:--> | |
167 | <mml:mrow> | |
168 | <mml:mrow> | |
169 | <mml:mo>Δ</mml:mo> | |
170 | <mml:mi mathvariant="italic">u</mml:mi> | |
171 | </mml:mrow> | |
172 | <mml:mo>=</mml:mo> | |
173 | <mml:mfrac> | |
174 | <mml:mfenced open="(" close=")"> | |
175 | <mml:mrow> | |
176 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
177 | <mml:mn>2</mml:mn> | |
178 | </mml:msub> | |
179 | <mml:mo>-</mml:mo> | |
180 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
181 | <mml:mn>1</mml:mn> | |
182 | </mml:msub> | |
183 | </mml:mrow> | |
184 | </mml:mfenced> | |
185 | <mml:mi mathvariant="italic">n</mml:mi> | |
186 | </mml:mfrac> | |
187 | </mml:mrow> | |
188 | </mml:math></informalequation> | |
189 | <para> | |
190 | <informalequation><mml:math> | |
191 | <!-- eqn: DELTA v = ( v sub 2 - v sub 1 ) / m:--> | |
192 | <mml:mrow> | |
193 | <mml:mrow> | |
194 | <mml:mo>Δ</mml:mo> | |
195 | <mml:mi mathvariant="italic">v</mml:mi> | |
196 | </mml:mrow> | |
197 | <mml:mo>=</mml:mo> | |
198 | <mml:mfrac> | |
199 | <mml:mfenced open="(" close=")"> | |
200 | <mml:mrow> | |
201 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
202 | <mml:mn>2</mml:mn> | |
203 | </mml:msub> | |
204 | <mml:mo>-</mml:mo> | |
205 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
206 | <mml:mn>1</mml:mn> | |
207 | </mml:msub> | |
208 | </mml:mrow> | |
209 | </mml:mfenced> | |
210 | <mml:mi mathvariant="italic">m</mml:mi> | |
211 | </mml:mfrac> | |
212 | </mml:mrow> | |
213 | </mml:math></informalequation> | |
214 | </para> | |
215 | </para> | |
216 | <para> | |
217 | where | |
218 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>, | |
219 | <inlineequation><mml:math> | |
220 | <!-- eqn: u sub 1:--> | |
221 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
222 | <mml:mn>1</mml:mn> | |
223 | </mml:msub> | |
224 | </mml:math></inlineequation>, | |
225 | <inlineequation><mml:math> | |
226 | <!-- eqn: u sub 2:--> | |
227 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
228 | <mml:mn>2</mml:mn> | |
229 | </mml:msub> | |
230 | </mml:math></inlineequation>, | |
231 | <inlineequation><mml:math><mml:mi mathvariant="italic">m</mml:mi></mml:math></inlineequation>, | |
232 | <inlineequation><mml:math> | |
233 | <!-- eqn: v sub 1:--> | |
234 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
235 | <mml:mn>1</mml:mn> | |
236 | </mml:msub> | |
237 | </mml:math></inlineequation>, | |
238 | and | |
239 | <inlineequation><mml:math> | |
240 | <!-- eqn: v sub 2:--> | |
241 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
242 | <mml:mn>2</mml:mn> | |
243 | </mml:msub> | |
244 | </mml:math></inlineequation> | |
245 | are the arguments to the most recent <citerefentry><refentrytitle>glMapGrid2</refentrytitle></citerefentry> command. | |
246 | Then the <function>glEvalPoint2</function> command is equivalent to calling | |
247 | <programlisting> | |
248 | glEvalCoord2( <mml:math> | |
249 | <!-- i \cdot DELTA u + u sub 1 :--> | |
250 | <mml:mrow> | |
251 | <mml:mrow> | |
252 | <mml:mn>i</mml:mn> | |
253 | <mml:mo>·</mml:mo> | |
254 | <mml:mo>Δ</mml:mo> | |
255 | <mml:mi mathvariant="italic">u</mml:mi> | |
256 | </mml:mrow> | |
257 | <mml:mo>+</mml:mo> | |
258 | <mml:msub> | |
259 | <mml:mi mathvariant="italic">u</mml:mi> | |
260 | <mml:mn>1</mml:mn> | |
261 | </mml:msub> | |
262 | <mml:mo>,</mml:mo> | |
263 | <!-- j \cdot DELTA v + v sub 1 :--> | |
264 | <mml:mrow> | |
265 | <mml:mn>j</mml:mn> | |
266 | <mml:mo>·</mml:mo> | |
267 | <mml:mo>Δ</mml:mo> | |
268 | <mml:mi mathvariant="italic">v</mml:mi> | |
269 | ||
270 | </mml:mrow> | |
271 | <mml:mo>+</mml:mo> | |
272 | <mml:msub> | |
273 | <mml:mi mathvariant="italic">v</mml:mi> | |
274 | <mml:mn>1</mml:mn> | |
275 | </mml:msub> | |
276 | </mml:mrow> | |
277 | </mml:math> ); | |
278 | </programlisting> | |
279 | The only absolute numeric requirements are that if | |
280 | <inlineequation><mml:math> | |
281 | <!-- eqn: i = n:--> | |
282 | <mml:mrow> | |
283 | <mml:mi mathvariant="italic">i</mml:mi> | |
284 | <mml:mo>=</mml:mo> | |
285 | <mml:mi mathvariant="italic">n</mml:mi> | |
286 | </mml:mrow> | |
287 | </mml:math></inlineequation>, | |
288 | then the value computed from | |
289 | <inlineequation><mml:math> | |
290 | <!-- eqn: i cdot DELTA u + u sub 1:--> | |
291 | <mml:mrow> | |
292 | <mml:mrow> | |
293 | <mml:mi mathvariant="italic">i</mml:mi> | |
294 | <mml:mo>·</mml:mo> | |
295 | <mml:mrow> | |
296 | <mml:mo>Δ</mml:mo> | |
297 | <mml:mi mathvariant="italic">u</mml:mi> | |
298 | </mml:mrow> | |
299 | </mml:mrow> | |
300 | <mml:mo>+</mml:mo> | |
301 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
302 | <mml:mn>1</mml:mn> | |
303 | </mml:msub> | |
304 | </mml:mrow> | |
305 | </mml:math></inlineequation> | |
306 | is exactly | |
307 | <inlineequation><mml:math> | |
308 | <!-- eqn: u sub 2:--> | |
309 | <mml:msub><mml:mi mathvariant="italic">u</mml:mi> | |
310 | <mml:mn>2</mml:mn> | |
311 | </mml:msub> | |
312 | </mml:math></inlineequation>, | |
313 | and if | |
314 | <inlineequation><mml:math> | |
315 | <!-- eqn: j = m:--> | |
316 | <mml:mrow> | |
317 | <mml:mi mathvariant="italic">j</mml:mi> | |
318 | <mml:mo>=</mml:mo> | |
319 | <mml:mi mathvariant="italic">m</mml:mi> | |
320 | </mml:mrow> | |
321 | </mml:math></inlineequation>, | |
322 | then the value computed from | |
323 | <inlineequation><mml:math> | |
324 | <!-- eqn: j cdot DELTA v + v sub 1:--> | |
325 | <mml:mrow> | |
326 | <mml:mrow> | |
327 | <mml:mi mathvariant="italic">j</mml:mi> | |
328 | <mml:mo>·</mml:mo> | |
329 | <mml:mrow> | |
330 | <mml:mo>Δ</mml:mo> | |
331 | <mml:mi mathvariant="italic">v</mml:mi> | |
332 | </mml:mrow> | |
333 | </mml:mrow> | |
334 | <mml:mo>+</mml:mo> | |
335 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
336 | <mml:mn>1</mml:mn> | |
337 | </mml:msub> | |
338 | </mml:mrow> | |
339 | </mml:math></inlineequation> | |
340 | is exactly | |
341 | <inlineequation><mml:math> | |
342 | <!-- eqn: v sub 2:--> | |
343 | <mml:msub><mml:mi mathvariant="italic">v</mml:mi> | |
344 | <mml:mn>2</mml:mn> | |
345 | </mml:msub> | |
346 | </mml:math></inlineequation>. | |
347 | </para> | |
348 | </refsect1> | |
349 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
350 | <para> | |
351 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP1_GRID_DOMAIN</constant> | |
352 | </para> | |
353 | <para> | |
354 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP2_GRID_DOMAIN</constant> | |
355 | </para> | |
356 | <para> | |
357 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP1_GRID_SEGMENTS</constant> | |
358 | </para> | |
359 | <para> | |
360 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP2_GRID_SEGMENTS</constant> | |
361 | </para> | |
362 | </refsect1> | |
363 | <refsect1 id="seealso"><title>See Also</title> | |
364 | <para> | |
365 | <citerefentry><refentrytitle>glEvalCoord</refentrytitle></citerefentry>, | |
366 | <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>, | |
367 | <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>, | |
368 | <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>, | |
369 | <citerefentry><refentrytitle>glMapGrid</refentrytitle></citerefentry> | |
370 | </para> | |
371 | </refsect1> | |
372 | <refsect1 id="Copyright"><title>Copyright</title> | |
373 | <para> | |
374 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
375 | Silicon Graphics, Inc. This document is licensed under the SGI | |
376 | Free Software B License. For details, see | |
377 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
378 | </para> | |
379 | </refsect1> | |
380 | </refentry> |