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