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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="glGetTexLevelParameter"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
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8 | <year>2013</year> |
9 | <holder>Khronos Group</holder> | |
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10 | </copyright> |
11 | </refmetainfo> | |
12 | <refentrytitle>glGetTexLevelParameter</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glGetTexLevelParameter</refname> | |
17 | <refpurpose>return texture parameter values for a specific level of detail</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glGetTexLevelParameterfv</function></funcdef> | |
23 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
24 | <paramdef>GLint <parameter>level</parameter></paramdef> | |
25 | <paramdef>GLenum <parameter>pname</parameter></paramdef> | |
26 | <paramdef>GLfloat * <parameter>params</parameter></paramdef> | |
27 | </funcprototype> | |
28 | </funcsynopsis> | |
29 | <funcsynopsis> | |
30 | <funcprototype> | |
31 | <funcdef>void <function>glGetTexLevelParameteriv</function></funcdef> | |
32 | <paramdef>GLenum <parameter>target</parameter></paramdef> | |
33 | <paramdef>GLint <parameter>level</parameter></paramdef> | |
34 | <paramdef>GLenum <parameter>pname</parameter></paramdef> | |
35 | <paramdef>GLint * <parameter>params</parameter></paramdef> | |
36 | </funcprototype> | |
37 | </funcsynopsis> | |
38 | </refsynopsisdiv> | |
39 | <!-- eqn: ignoring delim $$ --> | |
40 | <refsect1 id="parameters"><title>Parameters</title> | |
41 | <variablelist> | |
42 | <varlistentry> | |
43 | <term><parameter>target</parameter></term> | |
44 | <listitem> | |
45 | <para> | |
46 | Specifies the symbolic name of the target texture, | |
47 | one of | |
48 | <constant>GL_TEXTURE_1D</constant>, | |
49 | <constant>GL_TEXTURE_2D</constant>, | |
50 | <constant>GL_TEXTURE_3D</constant>, | |
51 | <constant>GL_TEXTURE_1D_ARRAY</constant>, | |
52 | <constant>GL_TEXTURE_2D_ARRAY</constant>, | |
53 | <constant>GL_TEXTURE_RECTANGLE</constant>, | |
54 | <constant>GL_TEXTURE_2D_MULTISAMPLE</constant>, | |
55 | <constant>GL_TEXTURE_2D_MULTISAMPLE_ARRAY</constant>, | |
56 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>, | |
57 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>, | |
58 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>, | |
59 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>, | |
60 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>, | |
61 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>, | |
62 | <constant>GL_PROXY_TEXTURE_1D</constant>, | |
63 | <constant>GL_PROXY_TEXTURE_2D</constant>, | |
64 | <constant>GL_PROXY_TEXTURE_3D</constant>, | |
65 | <constant>GL_PROXY_TEXTURE_1D_ARRAY</constant>, | |
66 | <constant>GL_PROXY_TEXTURE_2D_ARRAY</constant>, | |
67 | <constant>GL_PROXY_TEXTURE_RECTANGLE</constant>, | |
68 | <constant>GL_PROXY_TEXTURE_2D_MULTISAMPLE</constant>, | |
69 | <constant>GL_PROXY_TEXTURE_2D_MULTISAMPLE_ARRAY</constant>, | |
70 | <constant>GL_PROXY_TEXTURE_CUBE_MAP</constant>, or | |
71 | <constant>GL_TEXTURE_BUFFER</constant>. | |
72 | </para> | |
73 | </listitem> | |
74 | </varlistentry> | |
75 | <varlistentry> | |
76 | <term><parameter>level</parameter></term> | |
77 | <listitem> | |
78 | <para> | |
79 | Specifies the level-of-detail number of the desired image. | |
80 | Level 0 is the base image level. | |
81 | Level | |
82 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation> | |
83 | is the | |
84 | <inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th | |
85 | mipmap reduction image. | |
86 | </para> | |
87 | </listitem> | |
88 | </varlistentry> | |
89 | <varlistentry> | |
90 | <term><parameter>pname</parameter></term> | |
91 | <listitem> | |
92 | <para> | |
93 | Specifies the symbolic name of a texture parameter. | |
94 | <constant>GL_TEXTURE_WIDTH</constant>, | |
95 | <constant>GL_TEXTURE_HEIGHT</constant>, | |
96 | <constant>GL_TEXTURE_DEPTH</constant>, | |
97 | <constant>GL_TEXTURE_INTERNAL_FORMAT</constant>, | |
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98 | <constant>GL_TEXTURE_RED_SIZE</constant>, |
99 | <constant>GL_TEXTURE_GREEN_SIZE</constant>, | |
100 | <constant>GL_TEXTURE_BLUE_SIZE</constant>, | |
101 | <constant>GL_TEXTURE_ALPHA_SIZE</constant>, | |
102 | <constant>GL_TEXTURE_DEPTH_SIZE</constant>, | |
103 | <constant>GL_TEXTURE_COMPRESSED</constant>, | |
104 | <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant>, and | |
105 | <constant>GL_TEXTURE_BUFFER_OFFSET</constant> | |
106 | are accepted. | |
107 | </para> | |
108 | </listitem> | |
109 | </varlistentry> | |
110 | <varlistentry> | |
111 | <term><parameter>params</parameter></term> | |
112 | <listitem> | |
113 | <para> | |
114 | Returns the requested data. | |
115 | </para> | |
116 | </listitem> | |
117 | </varlistentry> | |
118 | </variablelist> | |
119 | </refsect1> | |
120 | <refsect1 id="description"><title>Description</title> | |
121 | <para> | |
122 | <function>glGetTexLevelParameter</function> returns in <parameter>params</parameter> texture parameter values for a specific | |
123 | level-of-detail value, | |
124 | specified as <parameter>level</parameter>. | |
125 | <parameter>target</parameter> defines the target texture, | |
126 | either <constant>GL_TEXTURE_1D</constant>, <constant>GL_TEXTURE_2D</constant>, <constant>GL_TEXTURE_3D</constant>, | |
127 | <constant>GL_PROXY_TEXTURE_1D</constant>, | |
128 | <constant>GL_PROXY_TEXTURE_2D</constant>, | |
129 | <constant>GL_PROXY_TEXTURE_3D</constant>, | |
130 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>, | |
131 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>, | |
132 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>, | |
133 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>, | |
134 | <constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>, | |
135 | <constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>, or | |
136 | <constant>GL_PROXY_TEXTURE_CUBE_MAP</constant>. | |
137 | </para> | |
138 | <para> | |
139 | <constant>GL_MAX_TEXTURE_SIZE</constant>, and <constant>GL_MAX_3D_TEXTURE_SIZE</constant> are not really | |
140 | descriptive enough. | |
141 | It has to report the largest square texture image that can be | |
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142 | accommodated with mipmaps |
143 | but a long skinny texture, or a texture without mipmaps may | |
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144 | easily fit in texture memory. |
145 | The proxy targets allow the user to more accurately query | |
146 | whether the GL can accommodate a texture of a given configuration. | |
147 | If the texture cannot be accommodated, the texture state variables, which | |
148 | may be queried with <function>glGetTexLevelParameter</function>, are set to 0. If the texture can be accommodated, | |
149 | the texture state values will be set as they would be set for a | |
150 | non-proxy target. | |
151 | </para> | |
152 | <para> | |
153 | <parameter>pname</parameter> specifies the texture parameter whose value or values | |
154 | will be returned. | |
155 | </para> | |
156 | <para> | |
157 | The accepted parameter names are as follows: | |
158 | </para> | |
159 | <variablelist> | |
160 | <varlistentry> | |
161 | <term><constant>GL_TEXTURE_WIDTH</constant></term> | |
162 | <listitem> | |
163 | <para> | |
164 | </para> | |
165 | <para> | |
166 | <parameter>params</parameter> returns a single value, | |
167 | the width of the texture image. | |
c7b31271 | 168 | The initial value is 0. |
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169 | </para> |
170 | </listitem> | |
171 | </varlistentry> | |
172 | <varlistentry> | |
173 | <term><constant>GL_TEXTURE_HEIGHT</constant></term> | |
174 | <listitem> | |
175 | <para> | |
176 | </para> | |
177 | <para> | |
178 | <parameter>params</parameter> returns a single value, | |
179 | the height of the texture image. | |
c7b31271 | 180 | The initial value is 0. |
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181 | </para> |
182 | </listitem> | |
183 | </varlistentry> | |
184 | <varlistentry> | |
185 | <term><constant>GL_TEXTURE_DEPTH</constant></term> | |
186 | <listitem> | |
187 | <para> | |
188 | </para> | |
189 | <para> | |
190 | <parameter>params</parameter> returns a single value, | |
191 | the depth of the texture image. | |
c7b31271 | 192 | The initial value is 0. |
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193 | </para> |
194 | </listitem> | |
195 | </varlistentry> | |
196 | <varlistentry> | |
197 | <term><constant>GL_TEXTURE_INTERNAL_FORMAT</constant></term> | |
198 | <listitem> | |
199 | <para> | |
200 | </para> | |
201 | <para> | |
202 | <parameter>params</parameter> returns a single value, | |
203 | the internal format of the texture image. | |
204 | </para> | |
205 | </listitem> | |
206 | </varlistentry> | |
207 | <varlistentry> | |
208 | <term><constant>GL_TEXTURE_RED_TYPE</constant>,</term> | |
209 | <listitem> | |
210 | </listitem> | |
211 | </varlistentry> | |
212 | <varlistentry> | |
213 | <term><constant>GL_TEXTURE_GREEN_TYPE</constant>,</term> | |
214 | <listitem> | |
215 | </listitem> | |
216 | </varlistentry> | |
217 | <varlistentry> | |
218 | <term><constant>GL_TEXTURE_BLUE_TYPE</constant>,</term> | |
219 | <listitem> | |
220 | </listitem> | |
221 | </varlistentry> | |
222 | <varlistentry> | |
223 | <term><constant>GL_TEXTURE_ALPHA_TYPE</constant>,</term> | |
224 | <listitem> | |
225 | </listitem> | |
226 | </varlistentry> | |
227 | <varlistentry> | |
228 | <term><constant>GL_TEXTURE_DEPTH_TYPE</constant></term> | |
229 | <listitem> | |
230 | <para> | |
231 | </para> | |
232 | <para> | |
233 | The data type used to store the component. | |
234 | The types <constant>GL_NONE</constant>, <constant>GL_SIGNED_NORMALIZED</constant>, | |
235 | <constant>GL_UNSIGNED_NORMALIZED</constant>, <constant>GL_FLOAT</constant>, | |
236 | <constant>GL_INT</constant>, and <constant>GL_UNSIGNED_INT</constant> may be returned | |
237 | to indicate signed normalized fixed-point, unsigned normalized fixed-point, floating-point, integer unnormalized, and | |
238 | unsigned integer unnormalized components, respectively. | |
239 | </para> | |
240 | </listitem> | |
241 | </varlistentry> | |
242 | <varlistentry> | |
243 | <term><constant>GL_TEXTURE_RED_SIZE</constant>,</term> | |
244 | <listitem> | |
245 | </listitem> | |
246 | </varlistentry> | |
247 | <varlistentry> | |
248 | <term><constant>GL_TEXTURE_GREEN_SIZE</constant>,</term> | |
249 | <listitem> | |
250 | </listitem> | |
251 | </varlistentry> | |
252 | <varlistentry> | |
253 | <term><constant>GL_TEXTURE_BLUE_SIZE</constant>,</term> | |
254 | <listitem> | |
255 | </listitem> | |
256 | </varlistentry> | |
257 | <varlistentry> | |
258 | <term><constant>GL_TEXTURE_ALPHA_SIZE</constant>,</term> | |
259 | <listitem> | |
260 | </listitem> | |
261 | </varlistentry> | |
262 | <varlistentry> | |
263 | <term><constant>GL_TEXTURE_DEPTH_SIZE</constant></term> | |
264 | <listitem> | |
265 | <para> | |
266 | </para> | |
267 | <para> | |
268 | The internal storage resolution of an individual component. | |
269 | The resolution chosen by the GL will be a close match for the resolution | |
270 | requested by the user with the component argument of <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>, | |
271 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>, and | |
272 | <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>. The initial value is 0. | |
273 | </para> | |
274 | </listitem> | |
275 | </varlistentry> | |
276 | <varlistentry> | |
277 | <term><constant>GL_TEXTURE_COMPRESSED</constant></term> | |
278 | <listitem> | |
279 | <para> | |
280 | </para> | |
281 | <para> | |
282 | <parameter>params</parameter> returns a single boolean value indicating if the texture image is | |
283 | stored in a compressed internal format. The initiali value is <constant>GL_FALSE</constant>. | |
284 | </para> | |
285 | </listitem> | |
286 | </varlistentry> | |
287 | <varlistentry> | |
288 | <term><constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant></term> | |
289 | <listitem> | |
290 | <para> | |
291 | </para> | |
292 | <para> | |
293 | <parameter>params</parameter> returns a single integer value, the number of unsigned bytes of the | |
294 | compressed texture image that would be returned from | |
295 | <citerefentry><refentrytitle>glGetCompressedTexImage</refentrytitle></citerefentry>. | |
296 | </para> | |
297 | </listitem> | |
298 | </varlistentry> | |
299 | <varlistentry> | |
300 | <term><constant>GL_TEXTURE_BUFFER_OFFSET</constant></term> | |
301 | <listitem> | |
302 | <para> | |
303 | </para> | |
304 | <para> | |
305 | <parameter>params</parameter> returns a single integer value, the offset into the | |
306 | data store of the buffer bound to a buffer texture. | |
307 | <citerefentry><refentrytitle>glTexBufferRange</refentrytitle></citerefentry>. | |
308 | </para> | |
309 | </listitem> | |
310 | </varlistentry> | |
311 | <varlistentry> | |
312 | <term><constant>GL_TEXTURE_BUFFER_SIZE</constant></term> | |
313 | <listitem> | |
314 | <para> | |
315 | </para> | |
316 | <para> | |
317 | <parameter>params</parameter> returns a single integer value, the size of the range of a | |
318 | data store of the buffer bound to a buffer texture. | |
319 | <citerefentry><refentrytitle>glTexBufferRange</refentrytitle></citerefentry>. | |
320 | </para> | |
321 | </listitem> | |
322 | </varlistentry> | |
323 | </variablelist> | |
324 | </refsect1> | |
325 | <refsect1 id="notes"><title>Notes</title> | |
326 | <para> | |
327 | If an error is generated, | |
328 | no change is made to the contents of <parameter>params</parameter>. | |
329 | </para> | |
330 | <para> | |
331 | <function>glGetTexLevelParameter</function> returns the texture level parameters for the active texture unit. | |
332 | </para> | |
333 | <para> | |
334 | <constant>GL_TEXTURE_BUFFER_OFFSET</constant> and <constant>GL_TEXTURE_BUFFER_SIZE</constant> are available only | |
335 | if the GL version is 4.3 or greater. | |
336 | </para> | |
337 | </refsect1> | |
338 | <refsect1 id="errors"><title>Errors</title> | |
339 | <para> | |
340 | <constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> or <parameter>pname</parameter> is not an | |
341 | accepted value. | |
342 | </para> | |
343 | <para> | |
344 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>level</parameter> is less than 0. | |
345 | </para> | |
346 | <para> | |
347 | <constant>GL_INVALID_VALUE</constant> may be generated if <parameter>level</parameter> is greater | |
348 | than | |
349 | <inlineequation><mml:math> | |
350 | <!-- eqn: log sub 2: --> | |
351 | <mml:msub><mml:mi mathvariant="italic">log</mml:mi> | |
352 | <mml:mn>2</mml:mn> | |
353 | </mml:msub> | |
354 | </mml:math></inlineequation> | |
355 | <emphasis>max</emphasis>, | |
356 | where <emphasis>max</emphasis> is the returned value of <constant>GL_MAX_TEXTURE_SIZE</constant>. | |
357 | </para> | |
358 | <para> | |
359 | <constant>GL_INVALID_VALUE</constant> is generated if <parameter>target</parameter> is <constant>GL_TEXTURE_BUFFER</constant> | |
360 | and <parameter>level</parameter> is not zero. | |
361 | </para> | |
362 | <para> | |
363 | <constant>GL_INVALID_OPERATION</constant> is generated if | |
364 | <constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant> is queried on texture images with an | |
365 | uncompressed internal format or on proxy targets. | |
366 | </para> | |
367 | </refsect1> | |
368 | <refsect1 id="seealso"><title>See Also</title> | |
369 | <para> | |
370 | <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>, | |
371 | <citerefentry><refentrytitle>glGetTexParameter</refentrytitle></citerefentry>, | |
372 | <citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>, | |
373 | <citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>, | |
374 | <citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>, | |
375 | <citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>, | |
376 | <citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>, | |
377 | <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>, | |
378 | <citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, | |
379 | <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>, | |
380 | <citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>, | |
381 | <citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>, | |
382 | <citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry>, | |
383 | <citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry> | |
384 | </para> | |
385 | </refsect1> | |
386 | <refsect1 id="Copyright"><title>Copyright</title> | |
387 | <para> | |
388 | Copyright <trademark class="copyright"></trademark> 1991-2006 | |
c7b31271 | 389 | Silicon Graphics, Inc. Copyright <trademark class="copyright"></trademark> 2010-2013 |
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390 | Khronos Group. This document is licensed under the SGI |
391 | Free Software B License. For details, see | |
392 | <ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>. | |
393 | </para> | |
394 | </refsect1> | |
395 | </refentry> |