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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glGetTexLevelParameter">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glGetTexLevelParameter</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glGetTexLevelParameter</refname>
<refpurpose>return texture parameter values for a specific level of detail</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glGetTexLevelParameterfv</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLint <parameter>level</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>GLfloat * <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glGetTexLevelParameteriv</function></funcdef>
<paramdef>GLenum <parameter>target</parameter></paramdef>
<paramdef>GLint <parameter>level</parameter></paramdef>
<paramdef>GLenum <parameter>pname</parameter></paramdef>
<paramdef>GLint * <parameter>params</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>target</parameter></term>
<listitem>
<para>
Specifies the symbolic name of the target texture,
either <constant>GL_TEXTURE_1D</constant>, <constant>GL_TEXTURE_2D</constant>, <constant>GL_TEXTURE_3D</constant>,
<constant>GL_PROXY_TEXTURE_1D</constant>, <constant>GL_PROXY_TEXTURE_2D</constant>,
<constant>GL_PROXY_TEXTURE_3D</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>, or
<constant>GL_PROXY_TEXTURE_CUBE_MAP</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>level</parameter></term>
<listitem>
<para>
Specifies the level-of-detail number of the desired image.
Level 0 is the base image level.
Level
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>
is the
<inlineequation><mml:math><mml:mi mathvariant="italic">n</mml:mi></mml:math></inlineequation>th
mipmap reduction image.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>pname</parameter></term>
<listitem>
<para>
Specifies the symbolic name of a texture parameter.
<constant>GL_TEXTURE_WIDTH</constant>,
<constant>GL_TEXTURE_HEIGHT</constant>,
<constant>GL_TEXTURE_DEPTH</constant>,
<constant>GL_TEXTURE_INTERNAL_FORMAT</constant>,
<constant>GL_TEXTURE_BORDER</constant>,
<constant>GL_TEXTURE_RED_SIZE</constant>,
<constant>GL_TEXTURE_GREEN_SIZE</constant>,
<constant>GL_TEXTURE_BLUE_SIZE</constant>,
<constant>GL_TEXTURE_ALPHA_SIZE</constant>,
<constant>GL_TEXTURE_LUMINANCE_SIZE</constant>,
<constant>GL_TEXTURE_INTENSITY_SIZE</constant>,
<constant>GL_TEXTURE_DEPTH_SIZE</constant>,
<constant>GL_TEXTURE_COMPRESSED</constant>, and
<constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant>
are accepted.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>params</parameter></term>
<listitem>
<para>
Returns the requested data.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glGetTexLevelParameter</function> returns in <parameter>params</parameter> texture parameter values for a specific
level-of-detail value,
specified as <parameter>level</parameter>.
<parameter>target</parameter> defines the target texture,
either <constant>GL_TEXTURE_1D</constant>, <constant>GL_TEXTURE_2D</constant>, <constant>GL_TEXTURE_3D</constant>,
<constant>GL_PROXY_TEXTURE_1D</constant>,
<constant>GL_PROXY_TEXTURE_2D</constant>,
<constant>GL_PROXY_TEXTURE_3D</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>, or
<constant>GL_PROXY_TEXTURE_CUBE_MAP</constant>.
</para>
<para>
<constant>GL_MAX_TEXTURE_SIZE</constant>, and <constant>GL_MAX_3D_TEXTURE_SIZE</constant> are not really
descriptive enough.
It has to report the largest square texture image that can be
accommodated with mipmaps and borders,
but a long skinny texture, or a texture without mipmaps and borders, may
easily fit in texture memory.
The proxy targets allow the user to more accurately query
whether the GL can accommodate a texture of a given configuration.
If the texture cannot be accommodated, the texture state variables, which
may be queried with <function>glGetTexLevelParameter</function>, are set to 0. If the texture can be accommodated,
the texture state values will be set as they would be set for a
non-proxy target.
</para>
<para>
<parameter>pname</parameter> specifies the texture parameter whose value or values
will be returned.
</para>
<para>
The accepted parameter names are as follows:
</para>
<variablelist>
<varlistentry>
<term><constant>GL_TEXTURE_WIDTH</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single value,
the width of the texture image.
This value includes the border of the texture image. The initial value is
0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_HEIGHT</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single value,
the height of the texture image.
This value includes the border of the texture image. The initial value is
0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_DEPTH</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single value,
the depth of the texture image.
This value includes the border of the texture image. The initial value is
0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_INTERNAL_FORMAT</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single value,
the internal format of the texture image.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_BORDER</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single value,
the width in pixels of the border of the texture image. The initial value
is 0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_RED_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_GREEN_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_BLUE_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_ALPHA_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_LUMINANCE_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_INTENSITY_SIZE</constant>,</term>
<listitem>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_DEPTH_SIZE</constant></term>
<listitem>
<para>
</para>
<para>
The internal storage resolution of an individual component.
The resolution chosen by the GL will be a close match for the resolution
requested by the user with the component argument of <citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>, <citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>, and
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>. The initial value is 0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_COMPRESSED</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single boolean value indicating if the texture image is
stored in a compressed internal format. The initiali value is <constant>GL_FALSE</constant>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant></term>
<listitem>
<para>
</para>
<para>
<parameter>params</parameter> returns a single integer value, the number of unsigned bytes of the
compressed texture image that would be returned from
<citerefentry><refentrytitle>glGetCompressedTexImage</refentrytitle></citerefentry>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
If an error is generated,
no change is made to the contents of <parameter>params</parameter>.
</para>
<para>
<constant>GL_TEXTURE_INTERNAL_FORMAT</constant> is available only if the GL version is
1.1 or greater. In version 1.0, use <constant>GL_TEXTURE_COMPONENTS</constant>
instead.
</para>
<para>
<constant>GL_PROXY_TEXTURE_1D</constant> and <constant>GL_PROXY_TEXTURE_2D</constant> are
available only if the GL version is 1.1 or greater.
</para>
<para>
<constant>GL_TEXTURE_3D</constant>, <constant>GL_PROXY_TEXTURE_3D</constant>, and <constant>GL_TEXTURE_DEPTH</constant>
are available only if the GL version is 1.2 or greater.
</para>
<para>
<constant>GL_TEXTURE_COMPRESSED</constant>,
<constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_X</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Y</constant>,
<constant>GL_TEXTURE_CUBE_MAP_POSITIVE_Z</constant>,
<constant>GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant>, and
<constant>GL_PROXY_TEXTURE_CUBE_MAP</constant> are available only if the GL version is 1.3
or greater.
</para>
<para>
For OpenGL versions 1.3 and greater, or when the <code>ARB_multitexture</code> extension is supported, <function>glGetTexLevelParameter</function> returns
the texture level parameters for the active texture unit.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_ENUM</constant> is generated if <parameter>target</parameter> or <parameter>pname</parameter> is not an
accepted value.
</para>
<para>
<constant>GL_INVALID_VALUE</constant> is generated if <parameter>level</parameter> is less than 0.
</para>
<para>
<constant>GL_INVALID_VALUE</constant> may be generated if <parameter>level</parameter> is greater
than
<inlineequation><mml:math>
<!-- eqn: log sub 2:-->
<mml:msub><mml:mi mathvariant="italic">log</mml:mi>
<mml:mn>2</mml:mn>
</mml:msub>
</mml:math></inlineequation>
<emphasis>max</emphasis>,
where <emphasis>max</emphasis> is the returned value of <constant>GL_MAX_TEXTURE_SIZE</constant>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glGetTexLevelParameter</function>
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if
<constant>GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant> is queried on texture images with an
uncompressed internal format or on proxy targets.
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glGetTexParameter</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexGen</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexSubImage1D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexSubImage2D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexSubImage3D</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glTexParameter</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006
Silicon Graphics, Inc. This document is licensed under the SGI
Free Software B License. For details, see
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
</para>
</refsect1>
</refentry>