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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" >
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<refentryinfo >
<copyright >
<year > 2013</year>
<holder > Khronos Group</holder>
</copyright>
</refentryinfo>
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<refmeta >
<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>
<refsect1 id= "parameters" > <title > Parameters</title>
<variablelist >
<varlistentry >
<term > <parameter > target</parameter> </term>
<listitem >
<para >
Specifies the symbolic name of the target texture,
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one of
<constant > GL_TEXTURE_1D</constant> ,
<constant > GL_TEXTURE_2D</constant> ,
<constant > GL_TEXTURE_3D</constant> ,
<constant > GL_TEXTURE_1D_ARRAY</constant> ,
<constant > GL_TEXTURE_2D_ARRAY</constant> ,
<constant > GL_TEXTURE_RECTANGLE</constant> ,
<constant > GL_TEXTURE_2D_MULTISAMPLE</constant> ,
<constant > GL_TEXTURE_2D_MULTISAMPLE_ARRAY</constant> ,
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<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> ,
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<constant > GL_TEXTURE_CUBE_MAP_NEGATIVE_Z</constant> ,
<constant > GL_PROXY_TEXTURE_1D</constant> ,
<constant > GL_PROXY_TEXTURE_2D</constant> ,
<constant > GL_PROXY_TEXTURE_3D</constant> ,
<constant > GL_PROXY_TEXTURE_1D_ARRAY</constant> ,
<constant > GL_PROXY_TEXTURE_2D_ARRAY</constant> ,
<constant > GL_PROXY_TEXTURE_RECTANGLE</constant> ,
<constant > GL_PROXY_TEXTURE_2D_MULTISAMPLE</constant> ,
<constant > GL_PROXY_TEXTURE_2D_MULTISAMPLE_ARRAY</constant> ,
<constant > GL_PROXY_TEXTURE_CUBE_MAP</constant> , or
<constant > GL_TEXTURE_BUFFER</constant> .
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</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.
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Level
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > n</mml:mi> </mml:math> </inlineequation>
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is the
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<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_RED_SIZE</constant> ,
<constant > GL_TEXTURE_GREEN_SIZE</constant> ,
<constant > GL_TEXTURE_BLUE_SIZE</constant> ,
<constant > GL_TEXTURE_ALPHA_SIZE</constant> ,
<constant > GL_TEXTURE_DEPTH_SIZE</constant> ,
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<constant > GL_TEXTURE_COMPRESSED</constant> ,
<constant > GL_TEXTURE_COMPRESSED_IMAGE_SIZE</constant> , and
<constant > GL_TEXTURE_BUFFER_OFFSET</constant>
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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
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accommodated with mipmaps
but a long skinny texture, or a texture without mipmaps may
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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 >
<parameter > params</parameter> returns a single value,
the width of the texture image.
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The initial value is 0.
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_HEIGHT</constant> </term>
<listitem >
<para >
<parameter > params</parameter> returns a single value,
the height of the texture image.
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The initial value is 0.
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_DEPTH</constant> </term>
<listitem >
<para >
<parameter > params</parameter> returns a single value,
the depth of the texture image.
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The initial value is 0.
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_INTERNAL_FORMAT</constant> </term>
<listitem >
<para >
<parameter > params</parameter> returns a single value,
the internal format of the texture image.
</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <constant > GL_TEXTURE_RED_TYPE</constant> ,
<constant > GL_TEXTURE_GREEN_TYPE</constant> ,
<constant > GL_TEXTURE_BLUE_TYPE</constant> ,
<constant > GL_TEXTURE_ALPHA_TYPE</constant> ,
<constant > GL_TEXTURE_DEPTH_TYPE</constant> </term>
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<listitem >
<para >
The data type used to store the component.
The types <constant > GL_NONE</constant> , <constant > GL_SIGNED_NORMALIZED</constant> ,
<constant > GL_UNSIGNED_NORMALIZED</constant> , <constant > GL_FLOAT</constant> ,
<constant > GL_INT</constant> , and <constant > GL_UNSIGNED_INT</constant> may be returned
to indicate signed normalized fixed-point, unsigned normalized fixed-point, floating-point, integer unnormalized, and
unsigned integer unnormalized components, respectively.
</para>
</listitem>
</varlistentry>
<varlistentry >
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<term > <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_DEPTH_SIZE</constant> </term>
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<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>
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<varlistentry >
<term > <constant > GL_TEXTURE_BUFFER_OFFSET</constant> </term>
<listitem >
<para >
</para>
<para >
<parameter > params</parameter> returns a single integer value, the offset into the
data store of the buffer bound to a buffer texture.
<citerefentry > <refentrytitle > glTexBufferRange</refentrytitle> </citerefentry> .
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_BUFFER_SIZE</constant> </term>
<listitem >
<para >
</para>
<para >
<parameter > params</parameter> returns a single integer value, the size of the range of a
data store of the buffer bound to a buffer texture.
<citerefentry > <refentrytitle > glTexBufferRange</refentrytitle> </citerefentry> .
</para>
</listitem>
</varlistentry>
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</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 >
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<function > glGetTexLevelParameter</function> returns the texture level parameters for the active texture unit.
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</para>
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<para >
<constant > GL_TEXTURE_BUFFER_OFFSET</constant> and <constant > GL_TEXTURE_BUFFER_SIZE</constant> are available only
if the GL version is 4.3 or greater.
</para>
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</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
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than
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<inlineequation > <mml:math >
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<!-- eqn: log sub 2: -->
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<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 >
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<constant > GL_INVALID_VALUE</constant> is generated if <parameter > target</parameter> is <constant > GL_TEXTURE_BUFFER</constant>
and <parameter > level</parameter> is not zero.
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</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 > 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
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Silicon Graphics, Inc. Copyright <trademark class= "copyright" > </trademark> 2010-2013
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Khronos Group. This document is licensed under the SGI
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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>
