upstream-man-pages/man2/xhtml/glGetTexLevelParameter.xml

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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>glGetTexLevelParameter</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /></head><body><div class="refentry" lang="en" xml:lang="en"><a id="glGetTexLevelParameter"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glGetTexLevelParameter — return texture parameter values for a specific level of detail</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">glGetTexLevelParameterfv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">level</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat *  </td><td><var class="pdparam">params</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">glGetTexLevelParameteriv</b>(</code></td><td>GLenum  </td><td><var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLint  </td><td><var class="pdparam">level</var>, </td></tr><tr><td> </td><td>GLenum  </td><td><var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint *  </td><td><var class="pdparam">params</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>target</code></em></span></dt><dd><p>
   4                     Specifies the symbolic name of the target texture,
   5                     either <code class="constant">GL_TEXTURE_1D</code>, <code class="constant">GL_TEXTURE_2D</code>, <code class="constant">GL_TEXTURE_3D</code>,
   6                     <code class="constant">GL_PROXY_TEXTURE_1D</code>, <code class="constant">GL_PROXY_TEXTURE_2D</code>,
   7                     <code class="constant">GL_PROXY_TEXTURE_3D</code>,
   8                     <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_X</code>,
   9                     <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_X</code>,
  10                     <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Y</code>,
  11                     <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</code>,
  12                     <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Z</code>,
  13                     <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</code>, or
  14                     <code class="constant">GL_PROXY_TEXTURE_CUBE_MAP</code>.
  15                 </p></dd><dt><span class="term"><em class="parameter"><code>level</code></em></span></dt><dd><p>
  16                     Specifies the level-of-detail number of the desired image.
  17                     Level 0 is the base image level.
  18                     Level
  19                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>
  20                     is the
  21                     <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"><mml:mi mathvariant="italic">n</mml:mi></mml:math>th
  22                     mipmap reduction image.
  23                 </p></dd><dt><span class="term"><em class="parameter"><code>pname</code></em></span></dt><dd><p>
  24                     Specifies the symbolic name of a texture parameter.
  25                     <code class="constant">GL_TEXTURE_WIDTH</code>,
  26                     <code class="constant">GL_TEXTURE_HEIGHT</code>,
  27                     <code class="constant">GL_TEXTURE_DEPTH</code>,
  28                     <code class="constant">GL_TEXTURE_INTERNAL_FORMAT</code>,
  29                     <code class="constant">GL_TEXTURE_BORDER</code>,
  30                     <code class="constant">GL_TEXTURE_RED_SIZE</code>,
  31                     <code class="constant">GL_TEXTURE_GREEN_SIZE</code>,
  32                     <code class="constant">GL_TEXTURE_BLUE_SIZE</code>,
  33                     <code class="constant">GL_TEXTURE_ALPHA_SIZE</code>,
  34                     <code class="constant">GL_TEXTURE_LUMINANCE_SIZE</code>,
  35                     <code class="constant">GL_TEXTURE_INTENSITY_SIZE</code>,
  36                     <code class="constant">GL_TEXTURE_DEPTH_SIZE</code>,
  37                     <code class="constant">GL_TEXTURE_COMPRESSED</code>, and
  38                     <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code>
  39                      are accepted.
  40                 </p></dd><dt><span class="term"><em class="parameter"><code>params</code></em></span></dt><dd><p>
  41                     Returns the requested data.
  42                 </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="description"></a><h2>Description</h2><p>
  43             <code class="function">glGetTexLevelParameter</code> returns in <em class="parameter"><code>params</code></em> texture parameter values for a specific
  44             level-of-detail value,
  45             specified as <em class="parameter"><code>level</code></em>.
  46             <em class="parameter"><code>target</code></em> defines the target texture,
  47             either <code class="constant">GL_TEXTURE_1D</code>, <code class="constant">GL_TEXTURE_2D</code>, <code class="constant">GL_TEXTURE_3D</code>,
  48             <code class="constant">GL_PROXY_TEXTURE_1D</code>,
  49             <code class="constant">GL_PROXY_TEXTURE_2D</code>,
  50             <code class="constant">GL_PROXY_TEXTURE_3D</code>,
  51             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_X</code>,
  52             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_X</code>,
  53             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Y</code>,
  54             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</code>,
  55             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Z</code>,
  56             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</code>, or
  57             <code class="constant">GL_PROXY_TEXTURE_CUBE_MAP</code>.
  58         </p><p>
  59             <code class="constant">GL_MAX_TEXTURE_SIZE</code>, and <code class="constant">GL_MAX_3D_TEXTURE_SIZE</code> are not really
  60             descriptive enough.
  61             It has to report the largest square texture image that can be
  62             accommodated with mipmaps and borders,
  63             but a long skinny texture, or a texture without mipmaps and borders, may
  64             easily fit in texture memory.
  65             The proxy targets allow the user to more accurately query
  66             whether the GL can accommodate a texture of a given configuration.
  67             If the texture cannot be accommodated, the texture state variables, which
  68             may be queried with <code class="function">glGetTexLevelParameter</code>, are set to 0.  If the texture can be accommodated,
  69             the texture state values will be set as they would be set for a
  70             non-proxy target.
  71         </p><p>
  72             <em class="parameter"><code>pname</code></em> specifies the texture parameter whose value or values
  73             will be returned.
  74         </p><p>
  75             The accepted parameter names are as follows:
  76         </p><div class="variablelist"><dl><dt><span class="term"><code class="constant">GL_TEXTURE_WIDTH</code></span></dt><dd><p>
  77                     </p><p>
  78                         <em class="parameter"><code>params</code></em> returns a single value,
  79                         the width of the texture image.
  80                         This value includes the border of the texture image. The initial value is
  81                         0.
  82                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_HEIGHT</code></span></dt><dd><p>
  83                     </p><p>
  84                         <em class="parameter"><code>params</code></em> returns a single value,
  85                         the height of the texture image.
  86                         This value includes the border of the texture image. The initial value is
  87                         0.
  88                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_DEPTH</code></span></dt><dd><p>
  89                     </p><p>
  90                         <em class="parameter"><code>params</code></em> returns a single value,
  91                         the depth of the texture image.
  92                         This value includes the border of the texture image. The initial value is
  93                         0.
  94                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_INTERNAL_FORMAT</code></span></dt><dd><p>
  95                     </p><p>
  96                         <em class="parameter"><code>params</code></em> returns a single value,
  97                         the internal format of the texture image.
  98                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_BORDER</code></span></dt><dd><p>
  99                     </p><p>
 100                         <em class="parameter"><code>params</code></em> returns a single value,
 101                         the width in pixels of the border of the texture image. The initial value
 102                         is 0.
 103                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_RED_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_GREEN_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_BLUE_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_ALPHA_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_LUMINANCE_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_INTENSITY_SIZE</code>,</span></dt><dd></dd><dt><span class="term"><code class="constant">GL_TEXTURE_DEPTH_SIZE</code></span></dt><dd><p>
 104                     </p><p>
 105                         The internal storage resolution of an individual component.
 106                         The resolution chosen by the GL will be a close match for the resolution
 107                         requested by the user with the component argument of <a class="citerefentry" href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a>,
 108                         <a class="citerefentry" href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>, <a class="citerefentry" href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a>, <a class="citerefentry" href="glCopyTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>, and
 109                         <a class="citerefentry" href="glCopyTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>. The initial value is 0.
 110                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_COMPRESSED</code></span></dt><dd><p>
 111                     </p><p>
 112                         <em class="parameter"><code>params</code></em> returns a single boolean value indicating if the texture image is
 113                         stored in a compressed internal format.  The initiali value is <code class="constant">GL_FALSE</code>.
 114                     </p></dd><dt><span class="term"><code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code></span></dt><dd><p>
 115                     </p><p>
 116                         <em class="parameter"><code>params</code></em> returns a single integer value, the number of unsigned bytes of the
 117                         compressed texture image that would be returned from
 118                         <a class="citerefentry" href="glGetCompressedTexImage.xml"><span class="citerefentry"><span class="refentrytitle">glGetCompressedTexImage</span></span></a>.
 119                     </p></dd></dl></div></div><div class="refsect1" lang="en" xml:lang="en"><a id="notes"></a><h2>Notes</h2><p>
 120             If an error is generated,
 121             no change is made to the contents of <em class="parameter"><code>params</code></em>.
 122         </p><p>
 123             <code class="constant">GL_TEXTURE_INTERNAL_FORMAT</code> is available only if the GL version is
 124             1.1 or greater. In version 1.0, use <code class="constant">GL_TEXTURE_COMPONENTS</code>
 125             instead.
 126         </p><p>
 127             <code class="constant">GL_PROXY_TEXTURE_1D</code> and <code class="constant">GL_PROXY_TEXTURE_2D</code> are
 128             available only if the GL version is 1.1 or greater.
 129         </p><p>
 130             <code class="constant">GL_TEXTURE_3D</code>, <code class="constant">GL_PROXY_TEXTURE_3D</code>, and <code class="constant">GL_TEXTURE_DEPTH</code>
 131             are available only if the GL version is 1.2 or greater.
 132         </p><p>
 133             <code class="constant">GL_TEXTURE_COMPRESSED</code>,
 134             <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code>,
 135             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_X</code>,
 136             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_X</code>,
 137             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Y</code>,
 138             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</code>,
 139             <code class="constant">GL_TEXTURE_CUBE_MAP_POSITIVE_Z</code>,
 140             <code class="constant">GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</code>, and
 141             <code class="constant">GL_PROXY_TEXTURE_CUBE_MAP</code> are available only if the GL version is 1.3
 142             or greater.
 143         </p><p>
 144             For OpenGL versions 1.3 and greater, or when the <code class="code">ARB_multitexture</code> extension is supported, <code class="function">glGetTexLevelParameter</code> returns
 145             the texture level parameters for the active texture unit.
 146         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="errors"></a><h2>Errors</h2><p>
 147             <code class="constant">GL_INVALID_ENUM</code> is generated if <em class="parameter"><code>target</code></em> or <em class="parameter"><code>pname</code></em> is not an
 148             accepted value.
 149         </p><p>
 150             <code class="constant">GL_INVALID_VALUE</code> is generated if <em class="parameter"><code>level</code></em> is less than 0.
 151         </p><p>
 152             <code class="constant">GL_INVALID_VALUE</code> may be generated if <em class="parameter"><code>level</code></em> is greater
 153             than
 154             <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
 155
 156                 <mml:msub><mml:mi mathvariant="italic">log</mml:mi>
 157                 <mml:mn>2</mml:mn>
 158                 </mml:msub>
 159             </mml:math>
 160             <span class="emphasis"><em>max</em></span>,
 161             where <span class="emphasis"><em>max</em></span> is the returned value of <code class="constant">GL_MAX_TEXTURE_SIZE</code>.
 162         </p><p>
 163             <code class="constant">GL_INVALID_OPERATION</code> is generated if <code class="function">glGetTexLevelParameter</code>
 164             is executed between the execution of <a class="citerefentry" href="glBegin.xml"><span class="citerefentry"><span class="refentrytitle">glBegin</span></span></a>
 165             and the corresponding execution of <a class="citerefentry" href="glEnd.xml"><span class="citerefentry"><span class="refentrytitle">glEnd</span></span></a>.
 166         </p><p>
 167             <code class="constant">GL_INVALID_OPERATION</code> is generated if
 168             <code class="constant">GL_TEXTURE_COMPRESSED_IMAGE_SIZE</code> is queried on texture images with an
 169             uncompressed internal format or on proxy targets.
 170         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="seealso"></a><h2>See Also</h2><p>
 171             <a class="citerefentry" href="glActiveTexture.xml"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>,
 172             <a class="citerefentry" href="glGetTexParameter.xml"><span class="citerefentry"><span class="refentrytitle">glGetTexParameter</span></span></a>,
 173             <a class="citerefentry" href="glCopyTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage1D</span></span></a>,
 174             <a class="citerefentry" href="glCopyTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>,
 175             <a class="citerefentry" href="glCopyTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage1D</span></span></a>,
 176             <a class="citerefentry" href="glCopyTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>,
 177             <a class="citerefentry" href="glCopyTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage3D</span></span></a>,
 178             <a class="citerefentry" href="glTexEnv.xml"><span class="citerefentry"><span class="refentrytitle">glTexEnv</span></span></a>,
 179             <a class="citerefentry" href="glTexGen.xml"><span class="citerefentry"><span class="refentrytitle">glTexGen</span></span></a>,
 180             <a class="citerefentry" href="glTexImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage1D</span></span></a>,
 181             <a class="citerefentry" href="glTexImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>,
 182             <a class="citerefentry" href="glTexImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexImage3D</span></span></a>,
 183             <a class="citerefentry" href="glTexSubImage1D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage1D</span></span></a>,
 184             <a class="citerefentry" href="glTexSubImage2D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage2D</span></span></a>,
 185             <a class="citerefentry" href="glTexSubImage3D.xml"><span class="citerefentry"><span class="refentrytitle">glTexSubImage3D</span></span></a>,
 186             <a class="citerefentry" href="glTexParameter.xml"><span class="citerefentry"><span class="refentrytitle">glTexParameter</span></span></a>
 187         </p></div><div class="refsect1" lang="en" xml:lang="en"><a id="Copyright"></a><h2>Copyright</h2><p>
 188             Copyright <span class="trademark"></span>© 1991-2006
 189             Silicon Graphics, Inc. This document is licensed under the SGI
 190             Free Software B License. For details, see
 191             <a class="ulink" href="http://oss.sgi.com/projects/FreeB/" target="_top">http://oss.sgi.com/projects/FreeB/</a>.
 192         </p></div></div></body></html>