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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= "glTexParameter" >
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<refentryinfo >
<copyright >
<year > 1991-2006</year>
<holder > Silicon Graphics, Inc.</holder>
</copyright>
</refentryinfo>
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<refmeta >
<refentrytitle > glTexParameter</refentrytitle>
<manvolnum > 3G</manvolnum>
</refmeta>
<refnamediv >
<refname > glTexParameter</refname>
<refpurpose > set texture parameters</refpurpose>
</refnamediv>
<refsynopsisdiv > <title > C Specification</title>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameterf</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > GLfloat <parameter > param</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameteri</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > GLint <parameter > param</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
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<!-- Vector commands -->
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<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameterfv</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > const GLfloat * <parameter > params</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameteriv</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > const GLint * <parameter > params</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
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<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameterIiv</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > const GLint * <parameter > params</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis >
<funcprototype >
<funcdef > void <function > glTexParameterIuiv</function> </funcdef>
<paramdef > GLenum <parameter > target</parameter> </paramdef>
<paramdef > GLenum <parameter > pname</parameter> </paramdef>
<paramdef > const GLuint * <parameter > params</parameter> </paramdef>
</funcprototype>
</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id= "parameters" > <title > Parameters</title>
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<variablelist >
<varlistentry >
<term > <parameter > target</parameter> </term>
<listitem >
<para >
Specifies the target texture,
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which must be either <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> ,
or <constant > GL_TEXTURE_CUBE_MAP</constant> .
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</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > pname</parameter> </term>
<listitem >
<para >
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Specifies the symbolic name of a single-valued texture parameter.
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<parameter > pname</parameter> can be one of the following:
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<constant > GL_DEPTH_STENCIL_TEXTURE_MODE</constant> ,
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<constant > GL_TEXTURE_BASE_LEVEL</constant> ,
<constant > GL_TEXTURE_COMPARE_FUNC</constant> ,
<constant > GL_TEXTURE_COMPARE_MODE</constant> ,
<constant > GL_TEXTURE_LOD_BIAS</constant> ,
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<constant > GL_TEXTURE_MIN_FILTER</constant> ,
<constant > GL_TEXTURE_MAG_FILTER</constant> ,
<constant > GL_TEXTURE_MIN_LOD</constant> ,
<constant > GL_TEXTURE_MAX_LOD</constant> ,
<constant > GL_TEXTURE_MAX_LEVEL</constant> ,
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<constant > GL_TEXTURE_SWIZZLE_R</constant> ,
<constant > GL_TEXTURE_SWIZZLE_G</constant> ,
<constant > GL_TEXTURE_SWIZZLE_B</constant> ,
<constant > GL_TEXTURE_SWIZZLE_A</constant> ,
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<constant > GL_TEXTURE_WRAP_S</constant> ,
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<constant > GL_TEXTURE_WRAP_T</constant> , or
<constant > GL_TEXTURE_WRAP_R</constant> .
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</para>
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<para >
For the vector commands
(<function > glTexParameter*v</function> ),
<parameter > pname</parameter> can also be one of
<constant > GL_TEXTURE_BORDER_COLOR</constant> or
<constant > GL_TEXTURE_SWIZZLE_RGBA</constant> .
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > param</parameter> </term>
<listitem >
<para >
For the scalar commands, specifies the value of
<parameter > pname</parameter> .
</para>
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</listitem>
</varlistentry>
<varlistentry >
<term > <parameter > params</parameter> </term>
<listitem >
<para >
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For the vector commands, specifies a pointer to an array
where the value or values of
<parameter > pname</parameter> are stored.
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</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id= "description" > <title > Description</title>
<para >
<function > glTexParameter</function> assigns the value or values in <parameter > params</parameter> to the texture parameter
specified as <parameter > pname</parameter> .
<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_1D_ARRAY</constant> ,
<constant > GL_TEXTURE_2D_ARRAY</constant> , <constant > GL_TEXTURE_RECTANGLE</constant> , or <constant > GL_TEXTURE_3D</constant> .
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The following symbols are accepted in <parameter > pname</parameter> :
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_DEPTH_STENCIL_TEXTURE_MODE</constant> </term>
<listitem >
<para >
Specifies the mode used to read from depth-stencil format textures. <parameter > params</parameter>
must be one of <constant > GL_DEPTH_COMPONENT</constant> or <constant > GL_STENCIL_COMPONENT</constant> .
If the depth stencil mode is <constant > GL_DEPTH_COMPONENT</constant> , then reads from depth-stencil
format textures will return the depth component of the texel in
<inlineequation > <mml:math > <mml:msub > <mml:mi > R</mml:mi> <mml:mi > t</mml:mi> </mml:msub> </mml:math> </inlineequation> and the stencil component
will be discarded. If the depth stencil mode is <constant > GL_STENCIL_COMPONENT</constant> then
the stencil component is returned in <inlineequation > <mml:math > <mml:msub > <mml:mi > R</mml:mi> <mml:mi > t</mml:mi> </mml:msub> </mml:math> </inlineequation>
and the depth component is discarded. The initial value is <constant > GL_DEPTH_COMPONENT</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
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<variablelist >
<varlistentry >
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<term > <constant > GL_TEXTURE_BASE_LEVEL</constant> </term>
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<listitem >
<para >
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Specifies the index of the lowest defined mipmap level. This is an
integer value. The initial value is 0.
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</para>
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</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_BORDER_COLOR</constant> </term>
<listitem >
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<para >
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The data in <parameter > params</parameter> specifies four values that define the border values that
should be used for border texels. If a texel is sampled from the border of the texture, the
values of <constant > GL_TEXTURE_BORDER_COLOR</constant> are interpreted as an RGBA color to match the
texture's internal format and substituted for the non-existent texel data. If the texture contains depth
components, the first component of <constant > GL_TEXTURE_BORDER_COLOR</constant> is interpreted as a depth value.
The initial value is
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<inlineequation > <mml:math >
<mml:mrow >
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<mml:mfenced open= "(" close= ")" >
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<mml:mrow >
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<mml:mn > 0.0</mml:mn>
<mml:mo > ,</mml:mo>
<mml:mn > 0.0</mml:mn>
<mml:mo > ,</mml:mo>
<mml:mn > 0.0</mml:mn>
<mml:mo > ,</mml:mo>
<mml:mn > 0.0</mml:mn>
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</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:math> </inlineequation> .
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</para>
<para >
If the values for <constant > GL_TEXTURE_BORDER_COLOR</constant> are specified with <function > glTexParameterIiv</function>
or <function > glTexParameterIuiv</function> , the values are stored unmodified with an internal data type of
integer. If specified with <function > glTexParameteriv</function> , they are converted to floating point with the following
equation:
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<inlineequation > <mml:math >
<mml:mrow >
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<mml:mi mathvariant= "italic" > f</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfrac >
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<mml:mrow >
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<mml:mn > 2</mml:mn>
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<mml:mi mathvariant= "italic" > c</mml:mi>
<mml:mo > +</mml:mo>
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<mml:mn > 1</mml:mn>
</mml:mrow>
<mml:mrow >
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<mml:msup >
<mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > b</mml:mi>
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</mml:msup>
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<mml:mo > -</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
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</mml:mfrac>
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</mml:mrow>
</mml:math> </inlineequation> .
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If specified with <function > glTexParameterfv</function> , they are stored unmodified as floating-point values.
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</para>
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</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_COMPARE_FUNC</constant> </term>
<listitem >
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<para >
Specifies the comparison operator used when <constant > GL_TEXTURE_COMPARE_MODE</constant> is
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set to <constant > GL_COMPARE_REF_TO_TEXTURE</constant> . Permissible values are:
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<informaltable frame= "topbot" >
<tgroup cols= "2" align= "left" >
<colspec />
<colspec />
<thead >
<row >
<entry rowsep= "1" align= "left" > <emphasis role= "bold" >
Texture Comparison Function
</emphasis> </entry>
<entry rowsep= "1" align= "left" > <emphasis role= "bold" >
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Computed result
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</emphasis> </entry>
</row>
</thead>
<tbody >
<row >
<entry align= "left" >
<constant > GL_LEQUAL</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > < =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > > </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_GEQUAL</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > > =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > < </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_LESS</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > < </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > > =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_GREATER</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > > </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > < =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_EQUAL</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > ≠ </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_NOTEQUAL</constant>
</entry>
<entry align= "left" >
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<inlineequation > <mml:math >
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<!-- eqn: result = left { cpile {1.0 above 0.0} lpile {r <= {D sub t} above r > {D sub t}}: -->
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<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "{" close= "" >
<mml:mrow >
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mn > 1.0</mml:mn>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mn > 0.0</mml:mn>
</mml:mtd> </mml:mtr>
</mml:mtable>
<mml:mo > ⁢ </mml:mo>
<mml:mtable >
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > ≠ </mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
<mml:mtr > <mml:mtd >
<mml:mrow >
<mml:mi mathvariant= "italic" > r</mml:mi>
<mml:mo > =</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:mfenced>
</mml:mrow>
</mml:mtd> </mml:mtr>
</mml:mtable>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
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</mml:math> </inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_ALWAYS</constant>
</entry>
<entry align= "left" >
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<inlineequation >
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<mml:math >
<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mi > 1.0</mml:mi>
</mml:mrow>
</mml:math>
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</inlineequation>
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</entry>
</row>
<row >
<entry align= "left" >
<constant > GL_NEVER</constant>
</entry>
<entry align= "left" >
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<inlineequation >
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<mml:math >
<mml:mrow >
<mml:mi mathvariant= "italic" > result</mml:mi>
<mml:mo > =</mml:mo>
<mml:mi > 0.0</mml:mi>
</mml:mrow>
</mml:math>
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</inlineequation>
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</entry>
</row>
</tbody>
</tgroup>
</informaltable>
where <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation>
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is the current interpolated texture coordinate, and
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<inlineequation > <mml:math >
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<!-- eqn: D sub t: -->
<mml:msub > <mml:mi mathvariant= "italic" > D</mml:mi>
<mml:mi mathvariant= "italic" > t</mml:mi>
</mml:msub>
</mml:math> </inlineequation>
is the depth texture value sampled from the currently bound depth texture.
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > result</mml:mi> </mml:math> </inlineequation>
is assigned to the the red channel.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_COMPARE_MODE</constant> </term>
<listitem >
<para >
Specifies the texture comparison mode for currently bound depth textures.
That is, a texture whose internal format is <constant > GL_DEPTH_COMPONENT_*</constant> ; see
<citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> )
Permissible values are:
<variablelist >
<varlistentry >
<term > <constant > GL_COMPARE_REF_TO_TEXTURE</constant> </term>
<listitem >
<para >
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Specifies that the interpolated and clamped
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation>
texture coordinate should
be compared to the value in the currently bound depth texture. See the
discussion of <constant > GL_TEXTURE_COMPARE_FUNC</constant> for details of how the comparison
is evaluated. The result of the comparison is assigned to the red channel.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_NONE</constant> </term>
<listitem >
<para >
Specifies that the red channel should be assigned the
appropriate value from the currently bound depth texture.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_LOD_BIAS</constant> </term>
<listitem >
<para >
<parameter > params</parameter> specifies a fixed bias value that is to be added to the level-of-detail
parameter for the texture before texture sampling. The specified value is added to the shader-supplied
bias value (if any) and subsequently clamped into the implementation-defined range
<inlineequation > <mml:math >
<mml:mfenced open= "[" close= "]" >
<mml:mfenced open= "" close= "" >
<mml:mrow >
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<mml:mo > -</mml:mo>
<mml:msub >
<mml:mi mathvariant= "italic" > bias</mml:mi>
<mml:mi mathvariant= "italic" > max</mml:mi>
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</mml:msub>
</mml:mrow>
</mml:mfenced>
<mml:mrow >
<mml:mfenced open= "" close= "" >
<mml:mrow >
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<mml:msub >
<mml:mi mathvariant= "italic" > bias</mml:mi>
<mml:mi mathvariant= "italic" > max</mml:mi>
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</mml:msub>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mfenced>
</mml:math> </inlineequation> ,
where
<inlineequation > <mml:math >
<mml:mrow >
<mml:msub > <mml:mi mathvariant= "italic" > bias</mml:mi>
<mml:mi mathvariant= "italic" > max</mml:mi>
</mml:msub>
</mml:mrow>
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</mml:math> </inlineequation>
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is the value of the implementation defined constant <constant > GL_MAX_TEXTURE_LOD_BIAS</constant> . The initial value is 0.0.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_TEXTURE_MIN_FILTER</constant> </term>
<listitem >
<para >
The texture minifying function is used whenever the level-of-detail function
used when sampling from the texture determines that the texture should be minified.
There are six defined minifying functions.
Two of them use either the nearest texture elements or a weighted average of multiple texture elements
to compute the texture value.
The other four use mipmaps.
</para>
<para >
A mipmap is an ordered set of arrays representing the same image
at progressively lower resolutions.
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If the texture has dimensions
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<inlineequation > <mml:math >
<!-- eqn: 2 sup n times 2 sup m: -->
<mml:mrow >
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > n</mml:mi>
</mml:msup>
<mml:mo > × </mml:mo>
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > m</mml:mi>
</mml:msup>
</mml:mrow>
</mml:math> </inlineequation> ,
there are
<inlineequation > <mml:math >
<!-- eqn: max ( n, m ) + 1: -->
<mml:mrow >
<mml:mrow >
<mml:mi mathvariant= "italic" > max</mml:mi>
<mml:mo > ⁡ </mml:mo>
<mml:mfenced open= "(" close= ")" >
<mml:mi mathvariant= "italic" > n</mml:mi>
<mml:mi mathvariant= "italic" > m</mml:mi>
</mml:mfenced>
</mml:mrow>
<mml:mo > +</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:math> </inlineequation>
mipmaps.
The first mipmap is the original texture,
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with dimensions
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<inlineequation > <mml:math >
<!-- eqn: 2 sup n times 2 sup m: -->
<mml:mrow >
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > n</mml:mi>
</mml:msup>
<mml:mo > × </mml:mo>
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > m</mml:mi>
</mml:msup>
</mml:mrow>
</mml:math> </inlineequation> .
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Each subsequent mipmap has dimensions
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<inlineequation > <mml:math >
<!-- eqn: 2 sup { k - 1 } times 2 sup { l - 1 }: -->
<mml:mrow >
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mi mathvariant= "italic" > k</mml:mi>
<mml:mo > -</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:msup>
<mml:mo > × </mml:mo>
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mi mathvariant= "italic" > l</mml:mi>
<mml:mo > -</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:msup>
</mml:mrow>
</mml:math> </inlineequation> ,
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where
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<inlineequation > <mml:math >
<!-- eqn: 2 sup k times 2 sup l: -->
<mml:mrow >
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > k</mml:mi>
</mml:msup>
<mml:mo > × </mml:mo>
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mi mathvariant= "italic" > l</mml:mi>
</mml:msup>
</mml:mrow>
</mml:math> </inlineequation>
are the dimensions of the previous mipmap,
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until either
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<inlineequation > <mml:math >
<!-- eqn: k = 0: -->
<mml:mrow >
<mml:mi mathvariant= "italic" > k</mml:mi>
<mml:mo > =</mml:mo>
<mml:mn > 0</mml:mn>
</mml:mrow>
</mml:math> </inlineequation>
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or
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<inlineequation > <mml:math >
<!-- eqn: l = 0: -->
<mml:mrow >
<mml:mi mathvariant= "italic" > l</mml:mi>
<mml:mo > =</mml:mo>
<mml:mn > 0</mml:mn>
</mml:mrow>
</mml:math> </inlineequation> .
At that point,
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subsequent mipmaps have dimension
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<inlineequation > <mml:math >
<!-- eqn: 1 times 2 sup { l - 1 }: -->
<mml:mrow >
<mml:mn > 1</mml:mn>
<mml:mo > × </mml:mo>
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mi mathvariant= "italic" > l</mml:mi>
<mml:mo > -</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:msup>
</mml:mrow>
</mml:math> </inlineequation>
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or
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<inlineequation > <mml:math >
<!-- eqn: 2 sup { k - 1} times 1: -->
<mml:mrow >
<mml:msup > <mml:mn > 2</mml:mn>
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mi mathvariant= "italic" > k</mml:mi>
<mml:mo > -</mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:mfenced>
</mml:msup>
<mml:mo > × </mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:math> </inlineequation>
until the final mipmap,
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which has dimension
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<inlineequation > <mml:math >
<!-- eqn: 1 times 1: -->
<mml:mrow >
<mml:mn > 1</mml:mn>
<mml:mo > × </mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:math> </inlineequation> .
To define the mipmaps, call <citerefentry > <refentrytitle > glTexImage1D</refentrytitle> </citerefentry> , <citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glTexImage3D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glCopyTexImage1D</refentrytitle> </citerefentry> , or <citerefentry > <refentrytitle > glCopyTexImage2D</refentrytitle> </citerefentry>
with the <emphasis > level</emphasis> argument indicating the order of the mipmaps.
Level 0 is the original texture;
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level
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<inlineequation > <mml:math >
<!-- eqn: max ( n, m ): -->
<mml:mrow >
<mml:mi mathvariant= "italic" > max</mml:mi>
<mml:mo > ⁡ </mml:mo>
<mml:mfenced open= "(" close= ")" >
<mml:mi mathvariant= "italic" > n</mml:mi>
<mml:mi mathvariant= "italic" > m</mml:mi>
</mml:mfenced>
</mml:mrow>
</mml:math> </inlineequation>
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is the final
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<inlineequation > <mml:math >
<!-- eqn: 1 times 1: -->
<mml:mrow >
<mml:mn > 1</mml:mn>
<mml:mo > × </mml:mo>
<mml:mn > 1</mml:mn>
</mml:mrow>
</mml:math> </inlineequation>
mipmap.
</para>
<para >
<parameter > params</parameter> supplies a function for minifying the texture as one of the
following:
<variablelist >
<varlistentry >
<term > <constant > GL_NEAREST</constant> </term>
<listitem >
<para >
Returns the value of the texture element that is nearest
(in Manhattan distance)
to the specified texture coordinates.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_LINEAR</constant> </term>
<listitem >
<para >
Returns the weighted average of the four texture elements
that are closest to the specified texture coordinates.
These can include items wrapped or repeated from other parts of a texture,
depending on the values of <constant > GL_TEXTURE_WRAP_S</constant> and <constant > GL_TEXTURE_WRAP_T</constant> ,
and on the exact mapping.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_NEAREST_MIPMAP_NEAREST</constant> </term>
<listitem >
<para >
Chooses the mipmap that most closely matches the size of the pixel
being textured and uses the <constant > GL_NEAREST</constant> criterion
(the texture element closest to the specified texture coordinates)
to produce a texture value.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_LINEAR_MIPMAP_NEAREST</constant> </term>
<listitem >
<para >
Chooses the mipmap that most closely matches the size of the pixel
being textured and uses the <constant > GL_LINEAR</constant> criterion
(a weighted average of the four texture elements that are closest to the specified texture coordinates)
to produce a texture value.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_NEAREST_MIPMAP_LINEAR</constant> </term>
<listitem >
<para >
Chooses the two mipmaps that most closely match the size of the pixel
being textured and uses the <constant > GL_NEAREST</constant> criterion
(the texture element closest to the specified texture coordinates )
to produce a texture value from each mipmap.
The final texture value is a weighted average of those two values.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_LINEAR_MIPMAP_LINEAR</constant> </term>
<listitem >
<para >
Chooses the two mipmaps that most closely match the size of the pixel
being textured and uses the <constant > GL_LINEAR</constant> criterion
(a weighted average of the texture elements that are closest to the specified texture coordinates)
to produce a texture value from each mipmap.
The final texture value is a weighted average of those two values.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
<para >
As more texture elements are sampled in the minification process,
fewer aliasing artifacts will be apparent.
While the <constant > GL_NEAREST</constant> and <constant > GL_LINEAR</constant> minification functions can be
faster than the other four,
they sample only one or multiple texture elements to determine the texture value
of the pixel being rendered and can produce moire patterns
or ragged transitions.
The initial value of <constant > GL_TEXTURE_MIN_FILTER</constant> is
<constant > GL_NEAREST_MIPMAP_LINEAR</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_MAG_FILTER</constant> </term>
<listitem >
<para >
The texture magnification function is used whenever the level-of-detail function
used when sampling from the texture determines that the texture should be magified.
It sets the texture magnification function to either <constant > GL_NEAREST</constant>
or <constant > GL_LINEAR</constant> (see below). <constant > GL_NEAREST</constant> is generally faster
than <constant > GL_LINEAR</constant> ,
but it can produce textured images with sharper edges
because the transition between texture elements is not as smooth.
The initial value of <constant > GL_TEXTURE_MAG_FILTER</constant> is <constant > GL_LINEAR</constant> .
<variablelist >
<varlistentry >
<term > <constant > GL_NEAREST</constant> </term>
<listitem >
<para >
Returns the value of the texture element that is nearest
(in Manhattan distance)
to the specified texture coordinates.
</para>
</listitem>
</varlistentry>
<varlistentry >
<term > <constant > GL_LINEAR</constant> </term>
<listitem >
<para >
Returns the weighted average of the texture elements
that are closest to the specified texture coordinates.
These can include items wrapped or repeated from other parts of a texture,
depending on the values of <constant > GL_TEXTURE_WRAP_S</constant> and <constant > GL_TEXTURE_WRAP_T</constant> ,
and on the exact mapping.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_MIN_LOD</constant> </term>
<listitem >
<para >
Sets the minimum level-of-detail parameter. This floating-point value
limits the selection of highest resolution mipmap (lowest mipmap
level). The initial value is -1000.
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</para>
</listitem>
</varlistentry>
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</variablelist>
<para >
</para>
<variablelist >
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<varlistentry >
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<term > <constant > GL_TEXTURE_MAX_LOD</constant> </term>
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<listitem >
<para >
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Sets the maximum level-of-detail parameter. This floating-point value
limits the selection of the lowest resolution mipmap (highest mipmap
level). The initial value is 1000.
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</para>
</listitem>
</varlistentry>
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</variablelist>
<para >
</para>
<variablelist >
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<varlistentry >
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<term > <constant > GL_TEXTURE_MAX_LEVEL</constant> </term>
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<listitem >
<para >
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Sets the index of the highest defined mipmap level. This is an integer
value. The initial value is 1000.
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_SWIZZLE_R</constant> </term>
<listitem >
<para >
Sets the swizzle that will be applied to the <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation>
component of a texel before it is returned to the shader. Valid values for <parameter > param</parameter> are <constant > GL_RED</constant> ,
<constant > GL_GREEN</constant> , <constant > GL_BLUE</constant> , <constant > GL_ALPHA</constant> , <constant > GL_ZERO</constant> and
<constant > GL_ONE</constant> .
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_RED</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be taken from the first
channel of the fetched texel.
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_GREEN</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be taken from the second
channel of the fetched texel.
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_BLUE</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be taken from the third
channel of the fetched texel.
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_ALPHA</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be taken from the fourth
channel of the fetched texel.
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_ZERO</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be subtituted with
<inlineequation > <mml:math > <mml:mn > 0.0</mml:mn> </mml:math> </inlineequation> .
If <constant > GL_TEXTURE_SWIZZLE_R</constant> is <constant > GL_ONE</constant> , the value for
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> will be subtituted with
<inlineequation > <mml:math > <mml:mn > 1.0</mml:mn> </mml:math> </inlineequation> .
The initial value is <constant > GL_RED</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_SWIZZLE_G</constant> </term>
<listitem >
<para >
Sets the swizzle that will be applied to the <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > g</mml:mi> </mml:math> </inlineequation>
component of a texel before it is returned to the shader. Valid values for <parameter > param</parameter> and their effects are similar to
those of <constant > GL_TEXTURE_SWIZZLE_R</constant> .
The initial value is <constant > GL_GREEN</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_SWIZZLE_B</constant> </term>
<listitem >
<para >
Sets the swizzle that will be applied to the <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > b</mml:mi> </mml:math> </inlineequation>
component of a texel before it is returned to the shader. Valid values for <parameter > param</parameter> and their effects are similar to
those of <constant > GL_TEXTURE_SWIZZLE_R</constant> .
The initial value is <constant > GL_BLUE</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_SWIZZLE_A</constant> </term>
<listitem >
<para >
Sets the swizzle that will be applied to the <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > a</mml:mi> </mml:math> </inlineequation>
component of a texel before it is returned to the shader. Valid values for <parameter > param</parameter> and their effects are similar to
those of <constant > GL_TEXTURE_SWIZZLE_R</constant> .
The initial value is <constant > GL_ALPHA</constant> .
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</para>
</listitem>
</varlistentry>
</variablelist>
<para >
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_SWIZZLE_RGBA</constant> </term>
<listitem >
<para >
Sets the swizzles that will be applied to the
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation> ,
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > g</mml:mi> </mml:math> </inlineequation> ,
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > b</mml:mi> </mml:math> </inlineequation> , and
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > a</mml:mi> </mml:math> </inlineequation>
components of a texel before they are returned to the shader. Valid values for <parameter > params</parameter> and their effects are similar to
those of <constant > GL_TEXTURE_SWIZZLE_R</constant> , except that all channels are specified simultaneously.
Setting the value of <constant > GL_TEXTURE_SWIZZLE_RGBA</constant> is equivalent (assuming no errors are generated) to
setting the parameters of each of <constant > GL_TEXTURE_SWIZZLE_R</constant> ,
<constant > GL_TEXTURE_SWIZZLE_G</constant> ,
<constant > GL_TEXTURE_SWIZZLE_B</constant> , and
<constant > GL_TEXTURE_SWIZZLE_A</constant> successively.
</para>
</listitem>
</varlistentry>
</variablelist>
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<para >
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_WRAP_S</constant> </term>
<listitem >
<para >
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Sets the wrap parameter for texture coordinate
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
to either <constant > GL_CLAMP_TO_EDGE</constant> , <constant > GL_CLAMP_TO_BORDER</constant> ,
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<constant > GL_MIRRORED_REPEAT</constant> ,
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<constant > GL_REPEAT</constant> , or <constant > GL_MIRROR_CLAMP_TO_EDGE</constant> . <constant > GL_CLAMP_TO_EDGE</constant> causes
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
coordinates to be clamped to the
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range
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<inlineequation > <mml:math >
<!-- eqn: left [ {1 over 2N}, 1 - {1 over 2N} right ]: -->
<mml:mfenced open= "[" close= "]" >
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mfrac >
<mml:mn > 1</mml:mn>
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<mml:mrow >
<mml:mn > 2</mml:mn> <mml:mi mathvariant= "italic" > N</mml:mi>
</mml:mrow>
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</mml:mfrac>
</mml:mrow>
</mml:mfenced>
<mml:mrow >
<mml:mn > 1</mml:mn>
<mml:mo > -</mml:mo>
<mml:mfenced open= "" close= "" >
<mml:mrow >
<mml:mfrac >
<mml:mn > 1</mml:mn>
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<mml:mrow >
<mml:mn > 2</mml:mn> <mml:mi mathvariant= "italic" > N</mml:mi>
</mml:mrow>
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</mml:mfrac>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
</mml:mfenced>
</mml:math> </inlineequation> ,
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where
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > N</mml:mi> </mml:math> </inlineequation>
is the size
of the texture in the direction of clamping.
<constant > GL_CLAMP_TO_BORDER</constant> evaluates <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation> coordinates in a similar manner to <constant > GL_CLAMP_TO_EDGE</constant> .
However, in cases where clamping would have occurred in <constant > GL_CLAMP_TO_EDGE</constant> mode, the fetched texel data
is substituted with the values specified by <constant > GL_TEXTURE_BORDER_COLOR</constant> .
<constant > GL_REPEAT</constant> causes the
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integer part of the
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
coordinate to be ignored; the GL uses only the
fractional part, thereby creating a repeating pattern.
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<constant > GL_MIRRORED_REPEAT</constant> causes the
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
coordinate to be set to the
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fractional part of the texture coordinate if the integer part of
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
is
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even; if the integer part of
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
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is odd, then the
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
texture coordinate is
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set to
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<inlineequation > <mml:math >
<!-- eqn: 1 - frac(s): -->
<mml:mrow >
<mml:mn > 1</mml:mn>
<mml:mo > -</mml:mo>
<mml:mrow >
<mml:mi mathvariant= "italic" > frac</mml:mi>
<mml:mo > ⁡ </mml:mo>
<mml:mfenced open= "(" close= ")" >
<mml:mi mathvariant= "italic" > s</mml:mi>
</mml:mfenced>
</mml:mrow>
</mml:mrow>
</mml:math> </inlineequation> ,
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where
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<inlineequation > <mml:math >
<!-- eqn: frac(s): -->
<mml:mrow >
<mml:mi mathvariant= "italic" > frac</mml:mi>
<mml:mo > ⁡ </mml:mo>
<mml:mfenced open= "(" close= ")" >
<mml:mi mathvariant= "italic" > s</mml:mi>
</mml:mfenced>
</mml:mrow>
</mml:math> </inlineequation>
represents the fractional part of
<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation> .
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<constant > GL_MIRROR_CLAMP_TO_EDGE</constant> causes the the <inlineequation > <mml:math > <mml:mi mathvariant= "italic" > s</mml:mi> </mml:math> </inlineequation>
coordinate to be repeated as for <constant > GL_MIRRORED_REPEAT</constant> for one reptition of the texture,
at which point the coordinate to be clamped as in <constant > GL_CLAMP_TO_EDGE</constant> .
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Initially, <constant > GL_TEXTURE_WRAP_S</constant> is set to <constant > GL_REPEAT</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
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<para >
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_WRAP_T</constant> </term>
<listitem >
<para >
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Sets the wrap parameter for texture coordinate
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > t</mml:mi> </mml:math> </inlineequation>
to either <constant > GL_CLAMP_TO_EDGE</constant> , <constant > GL_CLAMP_TO_BORDER</constant> ,
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<constant > GL_MIRRORED_REPEAT</constant> , <constant > GL_REPEAT</constant> , or
<constant > GL_MIRROR_CLAMP_TO_EDGE</constant> . See the discussion under <constant > GL_TEXTURE_WRAP_S</constant> .
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Initially, <constant > GL_TEXTURE_WRAP_T</constant> is set to <constant > GL_REPEAT</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
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<para >
</para>
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<variablelist >
<varlistentry >
<term > <constant > GL_TEXTURE_WRAP_R</constant> </term>
<listitem >
<para >
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Sets the wrap parameter for texture coordinate
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<inlineequation > <mml:math > <mml:mi mathvariant= "italic" > r</mml:mi> </mml:math> </inlineequation>
to either <constant > GL_CLAMP_TO_EDGE</constant> , <constant > GL_CLAMP_TO_BORDER</constant> ,
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<constant > GL_MIRRORED_REPEAT</constant> , <constant > GL_REPEAT</constant> , or
<constant > GL_MIRROR_CLAMP_TO_EDGE</constant> . See the discussion under <constant > GL_TEXTURE_WRAP_S</constant> .
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Initially, <constant > GL_TEXTURE_WRAP_R</constant> is set to <constant > GL_REPEAT</constant> .
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id= "notes" > <title > Notes</title>
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<para >
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Suppose that a program attempts to sample from a texture and
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has set <constant > GL_TEXTURE_MIN_FILTER</constant> to one of the functions that requires a
mipmap. If either the dimensions of the texture images currently defined
(with previous calls to <citerefentry > <refentrytitle > glTexImage1D</refentrytitle> </citerefentry> , <citerefentry > <refentrytitle > glTexImage2D</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glTexImage3D</refentrytitle> </citerefentry> , <citerefentry > <refentrytitle > glCopyTexImage1D</refentrytitle> </citerefentry> , or <citerefentry > <refentrytitle > glCopyTexImage2D</refentrytitle> </citerefentry> ) do not
follow the proper sequence for mipmaps (described above), or there are
fewer texture images defined than are needed, or the set of texture images
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have differing numbers of texture components, then the texture is considered <emphasis > incomplete</emphasis> .
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</para>
<para >
Linear filtering accesses the four nearest texture elements only in 2D
textures. In 1D textures, linear filtering accesses the two nearest
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texture elements. In 3D textures, linear filtering accesses the eight nearest
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texture elements.
</para>
<para >
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<function > glTexParameter</function> specifies the texture parameters for the active texture unit, specified
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by calling <citerefentry > <refentrytitle > glActiveTexture</refentrytitle> </citerefentry> .
</para>
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<para >
<constant > GL_DEPTH_STENCIL_TEXTURE_MODE</constant> is available only if the GL version is 4.3 or greater.
</para>
<para >
<constant > GL_MIRROR_CLAMP_TO_EDGE</constant> is available only if the GL version is 4.4 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
one of the accepted defined values.
</para>
<para >
<constant > GL_INVALID_ENUM</constant> is generated if <parameter > params</parameter> should have a defined
constant value (based on the value of <parameter > pname</parameter> ) and does not.
</para>
</refsect1>
<refsect1 id= "associatedgets" > <title > Associated Gets</title>
<para >
<citerefentry > <refentrytitle > glGetTexParameter</refentrytitle> </citerefentry>
</para>
<para >
<citerefentry > <refentrytitle > glGetTexLevelParameter</refentrytitle> </citerefentry>
</para>
</refsect1>
<refsect1 id= "seealso" > <title > See Also</title>
<para >
<citerefentry > <refentrytitle > glActiveTexture</refentrytitle> </citerefentry> ,
<citerefentry > <refentrytitle > glBindTexture</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 > glPixelStore</refentrytitle> </citerefentry> ,
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<citerefentry > <refentrytitle > glSamplerParameter</refentrytitle> </citerefentry> ,
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<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>
</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> 2012-2013
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>
