<div class="refentry" title="glTexParameter"><a id="glTexParameter"></a><div class="titlepage"></div><div class="refnamediv"><h2>Name</h2><p>glTexParameter — set texture parameters</p></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameterf</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat <var class="pdparam">param</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameteri</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint <var class="pdparam">param</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameterx</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfixed <var class="pdparam">param</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">

<em class="parameter"><code>target</code></em>

</span></dt><dd><p>Specifies the target texture, which must be

<code class="constant">GL_TEXTURE_2D</code>.</p></dd><dt><span class="term">

<em class="parameter"><code>pname</code></em>

</span></dt><dd><p>Specifies the symbolic name of a single-valued texture

parameter. Which can be one of the following:

<code class="constant">GL_TEXTURE_MIN_FILTER</code>,

<code class="constant">GL_TEXTURE_MAG_FILTER</code>,

<code class="constant">GL_TEXTURE_WRAP_S</code>,

<code class="constant">GL_TEXTURE_WRAP_T</code>, or

<code class="constant">GL_GENERATE_MIPMAP</code>.</p></dd><dt><span class="term">

<em class="parameter"><code>param</code></em>

</span></dt><dd><p>Specifies the value of <em class="parameter"><code>pname</code></em>.</p></dd></dl></div></div><div class="refsynopsisdiv" title="C Specification"><h2>C Specification</h2><div class="funcsynopsis"><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameterfv</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfloat * <var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameteriv</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLint * <var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div><table class="funcprototype-table"><tr><td><code class="funcdef">void <b class="fsfunc">glTexParameterxv</b>(</code></td><td>GLenum <var class="pdparam">target</var>, </td></tr><tr><td> </td><td>GLenum <var class="pdparam">pname</var>, </td></tr><tr><td> </td><td>GLfixed * <var class="pdparam">params</var><code>)</code>;</td></tr></table><div class="funcprototype-spacer"> </div></div></div><div class="refsect1" title="Parameters"><a id="parameters2"></a><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term">

<em class="parameter"><code>target</code></em>

</span></dt><dd><p>Specifies the target texture, which must be

<code class="constant">GL_TEXTURE_2D</code>.</p></dd><dt><span class="term">

<em class="parameter"><code>pname</code></em>

</span></dt><dd><p>Specifies the symbolic name of a texture parameter. Which can

be one of the following: <code class="constant">GL_TEXTURE_MIN_FILTER</code>,

<code class="constant">GL_TEXTURE_MAG_FILTER</code>,

<code class="constant">GL_TEXTURE_WRAP_S</code>,

<code class="constant">GL_TEXTURE_WRAP_T</code>, or

<code class="constant">GL_GENERATE_MIPMAP</code>.</p></dd><dt><span class="term">

<em class="parameter"><code>params</code></em>

</span></dt><dd><p>Specifies a pointer to an array where the value or values of

<em class="parameter"><code>pname</code></em> are stored.</p></dd></dl></div></div><div class="refsect1" title="Description"><a id="description"></a><h2>Description</h2><p>Texture mapping is a technique that applies an image onto an

object's surface as if the image were a decal or cellophane shrink-wrap.

The image is created in texture space, with an <math overflow="scroll">

<mfenced>

<mi>s</mi>

<mi>t</mi>

</mfenced>

</math> coordinate system. A texture is a one- or

two-dimensional image and a set of parameters that determine how samples

are derived from the image.</p><p><code class="function">glTexParameter</code> assigns the value in

<em class="parameter"><code>param</code></em> or <em class="parameter"><code>params</code></em> to the

texture parameter specified as <em class="parameter"><code>pname</code></em>.

<em class="parameter"><code>target</code></em> defines the target texture, which must be

<code class="constant">GL_TEXTURE_2D</code>.</p><p>The following symbols are accepted in

<em class="parameter"><code>pname</code></em>:</p><div class="variablelist"><dl><dt><span class="term">

<code class="constant">GL_TEXTURE_MIN_FILTER</code>

</span></dt><dd><p>The texture minifying function is used whenever the pixel

being textured maps to an area greater than one texture element.

There are six defined minifying functions. Two of them use the

nearest one or nearest four texture elements to compute the texture

value. The other four use mipmaps.</p><p>A mipmap is an ordered set of arrays representing the same

image at progressively lower resolutions. If the texture has

dimensions <math overflow="scroll">

<msup>

<mn>2</mn>

<mi>n</mi>

</msup>

<mo>x</mo>

<msup>

<mn>2</mn>

<mi>m</mi>

</msup>

</math>, there are <math overflow="scroll">

<mo>max</mo>

<mfenced>

<mi>n</mi>

<mi>m</mi>

</mfenced>

<mo>+</mo>

<mn>1</mn>

</math> mipmaps. The first mipmap is the original

texture, with dimensions <math overflow="scroll">

<msup>

<mn>2</mn>

<mi>n</mi>

</msup>

<mo>x</mo>

<msup>

<mn>2</mn>

<mi>m</mi>

</msup>

</math>. Each subsequent mipmap has dimensions

<math overflow="scroll">

<msup>

<mn>2</mn>

<mrow>

<mi>k</mi>

<mo>-</mo>

<mn>1</mn>

</mrow>

</msup>

<mo>x</mo>

<msup>

<mn>2</mn>

<mrow>

<mi>l</mi>

<mo>-</mo>

<mn>1</mn>

</mrow>

</msup>

</math>, where <math overflow="scroll">

<msup>

<mn>2</mn>

<mi>k</mi>

</msup>

<mo>x</mo>

<msup>

<mn>2</mn>

<mi>l</mi>

</msup>

</math> are the dimensions of the previous mipmap, until

either <math overflow="scroll">

<mi>k</mi>

<mo>=</mo>

<mn>0</mn>

</math> or <math overflow="scroll">

<mi>l</mi>

<mo>=</mo>

<mn>0</mn>

</math>. At that point, subsequent mipmaps have

dimension <math overflow="scroll">

<mn>1</mn>

<mo>x</mo>

<msup>

<mn>2</mn>

<mrow>

<mi>l</mi>

<mo>-</mo>

<mn>1</mn>

</mrow>

</msup>

</math> or <math overflow="scroll">

<msup>

<mn>2</mn>

<mrow>

<mi>k</mi>

<mo>-</mo>

<mn>1</mn>

</mrow>

</msup>

<mo>x</mo>

<mn>1</mn>

</math> until the final mipmap, which has dimension

<math overflow="scroll">

<mn>1</mn>

<mo>x</mo>

<mn>1</mn>

</math>. To define the mipmaps, call <a class="citerefentry" href="glTexImage2D"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a> or <a class="citerefentry" href="glCopyTexImage2D"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a> with the <em class="parameter"><code>level</code></em> argument

indicating the order of the mipmaps. Level 0 is the original

texture. Level <math overflow="scroll">

<mo>max</mo>

<mfenced>

<mi>n</mi>

<mi>m</mi>

</mfenced>

</math> is the final <math overflow="scroll">

<mn>1</mn>

<mo>x</mo>

<mn>1</mn>

</math> mipmap.</p><p><em class="parameter"><code>param</code></em> supplies a function for minifying

the texture as one of the following:</p><p>

</p><div class="variablelist"><dl><dt><span class="term">

<code class="constant">GL_NEAREST</code>

</span></dt><dd><p>Returns the value of the texture element that is nearest (in

Manhattan distance) to the center of the pixel being

textured.</p></dd><dt><span class="term">

<code class="constant">GL_LINEAR</code>

</span></dt><dd><p>Returns the weighted average of the four texture elements

that are closest to the center of the pixel being textured. These

can include repeated or wrapped elements, depending on the values

of <code class="constant">GL_TEXTURE_WRAP_S</code> and

<code class="constant">GL_TEXTURE_WRAP_T</code>, and on the exact

mapping.</p></dd><dt><span class="term">

<code class="constant">GL_NEAREST_MIPMAP_NEAREST</code>

</span></dt><dd><p>Chooses the mipmap that most closely matches the size of the

pixel being textured and uses the <code class="constant">GL_NEAREST</code>

criterion (the texture element nearest to the center of the pixel)

to produce a texture value.</p></dd><dt><span class="term">

<code class="constant">GL_LINEAR_MIPMAP_NEAREST</code>

</span></dt><dd><p>Chooses the mipmap that most closely matches the size of the

pixel being textured and uses the <code class="constant">GL_LINEAR</code>

criterion (a weighted average of the four texture elements that

are closest to the center of the pixel) to produce a texture

value.</p></dd><dt><span class="term">

<code class="constant">GL_NEAREST_MIPMAP_LINEAR</code>

</span></dt><dd><p>Chooses the two mipmaps that most closely match the size of

the pixel being textured and uses the

<code class="constant">GL_NEAREST</code> criterion (the texture element

nearest to the center of the pixel) to produce a texture value

from each mipmap. The final texture value is a weighted average of

those two values.</p></dd><dt><span class="term">

<code class="constant">GL_LINEAR_MIPMAP_LINEAR</code>

</span></dt><dd><p>Chooses the two mipmaps that most closely match the size of

the pixel being textured and uses the

<code class="constant">GL_LINEAR</code> criterion (a weighted average of

the four texture elements that are closest to the center of the

pixel) to produce a texture value from each mipmap. The final

texture value is a weighted average of those two values.</p><p>As more texture elements are sampled in the minification

process, fewer aliasing artifacts will be apparent. While the

<code class="constant">GL_NEAREST</code> and <code class="constant">GL_LINEAR</code>

minification functions can be faster than the other four, they

sample only one or four texture elements to determine the texture

value of the pixel being rendered and can produce moire patterns

or ragged transitions.</p></dd></dl></div><p>

</p><p>The initial value of <code class="constant">GL_TEXTURE_MIN_FILTER</code> is

<code class="constant">GL_NEAREST_MIPMAP_LINEAR</code>.</p></dd><dt><span class="term">

<code class="constant">GL_TEXTURE_MAG_FILTER</code>

</span></dt><dd><p>The texture magnification function is used when the pixel

being textured maps to an area less than or equal to one texture

element. It sets the texture magnification function to either

<code class="constant">GL_NEAREST</code> or <code class="constant">GL_LINEAR</code>

(see below). <code class="constant">GL_NEAREST</code> is generally faster

than <code class="constant">GL_LINEAR</code>, but it can produce textured

images with sharper edges because the transition between texture

elements is not as smooth.</p><p>

</p><div class="variablelist"><dl><dt><span class="term">

<code class="constant">GL_NEAREST</code>

</span></dt><dd><p>Returns the value of the texture element that is nearest (in

Manhattan distance) to the center of the pixel being

textured.</p></dd><dt><span class="term">

<code class="constant">GL_LINEAR</code>

</span></dt><dd><p>Returns the weighted average of the four texture elements

that are closest to the center of the pixel being textured. These

can include repeated or wrapped elements, depending on the values

of <code class="constant">GL_TEXTURE_WRAP_S</code> and

<code class="constant">GL_TEXTURE_WRAP_T</code>, and on the exact

mapping.</p></dd></dl></div><p>

</p><p>The initial value of <code class="constant">GL_TEXTURE_MAG_FILTER</code> is

<code class="constant">GL_LINEAR</code>.</p></dd><dt><span class="term">

<code class="constant">GL_TEXTURE_WRAP_S</code>

</span></dt><dd><p>Sets the wrap parameter for texture coordinate

<em class="replaceable"><code>s</code></em> to either

<code class="constant">GL_CLAMP_TO_EDGE</code> or

<code class="constant">GL_REPEAT</code>.</p><p>

</p><div class="variablelist"><dl><dt><span class="term">

<code class="constant">GL_CLAMP_TO_EDGE</code>

</span></dt><dd><p>causes <em class="replaceable"><code>s</code></em> coordinates to be

clamped to the range <math overflow="scroll">

<mo>[</mo>

<mfrac>

<mn>1</mn>

<mrow>

<mn>2</mn>

<mi>N</mi>

</mrow>

</mfrac>

<mo>,</mo>

<mn>1</mn>

<mo>-</mo>

<mfrac>

<mn>1</mn>

<mrow>

<mn>2</mn>

<mi>N</mi>

</mrow>

</mfrac>

<mo>]</mo>

</math>, where <em class="replaceable"><code>N</code></em> is the

size of the texture in the direction of clamping.</p></dd><dt><span class="term">

<code class="constant">GL_REPEAT</code>

</span></dt><dd><p>causes the integer part of the

<em class="replaceable"><code>s</code></em> coordinate to be ignored; the GL

uses only the fractional part, thereby creating a repeating

pattern.</p></dd></dl></div><p>

</p><p>The initial value of <code class="constant">GL_TEXTURE_WRAP_S</code> is

<code class="constant">GL_REPEAT</code>.</p></dd><dt><span class="term">

<code class="constant">GL_TEXTURE_WRAP_T</code>

</span></dt><dd><p>Sets the wrap parameter for texture coordinate

<em class="replaceable"><code>t</code></em> to either

<code class="constant">GL_CLAMP_TO_EDGE</code> or

<code class="constant">GL_REPEAT</code>. See the discussion under

<code class="constant">GL_TEXTURE_WRAP_S</code>.</p><p>The initial value of <code class="constant">GL_TEXTURE_WRAP_T</code> is

<code class="constant">GL_REPEAT</code>.</p></dd><dt><span class="term">

<code class="constant">GL_GENERATE_MIPMAP</code>

</span></dt><dd><p>Sets the automatic mipmap generation parameter. If set to

<code class="constant">GL_TRUE</code>, making any change to the interior

texels of the <math overflow="scroll">

<msub>

<mi>level</mi>

<mi>base</mi>

</msub>

</math> array of a mipmap will also compute a complete

set of mipmap arrays derived from the modified <math overflow="scroll">

<msub>

<mi>level</mi>

<mi>base</mi>

</msub>

</math> array. Array levels <math overflow="scroll"><msub>

<mi>level</mi>

<mi>base</mi>

</msub> <mo>+</mo><mi>1</mi> through

<mi>p</mi></math> are replaced with the derived arrays, regardless

of their previous contents. All other mipmap arrays, including the

<math overflow="scroll">

<msub>

<mi>level</mi>

<mi>base</mi>

</msub>

</math> array, are left unchanged by this

computation.</p><p>The initial value of <code class="constant">GL_GENERATE_MIPMAP</code>

is <code class="constant">GL_FALSE</code>.</p></dd></dl></div></div><div class="refsect1" title="Notes"><a id="notes"></a><h2>Notes</h2><p>Suppose that a program has enabled texturing (by calling

<a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a> with argument <code class="constant">GL_TEXTURE_2D</code> and has

set <code class="constant">GL_TEXTURE_MIN_FILTER</code> to one of the functions

that requires a mipmap. If either the dimensions of the texture images

currently defined (with previous calls to <a class="citerefentry" href="glTexImage2D"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>, or <a class="citerefentry" href="glCopyTexImage2D"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>) 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 have differing numbers of texture

components, then it is as if texture mapping were disabled.</p><p>Linear filtering accesses the four nearest texture elements.</p><p><code class="function">glTexParameter</code> specifies the texture parameters

for the texture bound to the active texture unit, specified by calling <a class="citerefentry" href="glActiveTexture"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>.</p></div><div class="refsect1" title="Errors"><a id="errors"></a><h2>Errors</h2><p><code class="constant">GL_INVALID_ENUM</code> is generated if

<em class="parameter"><code>target</code></em> or <em class="parameter"><code>pname</code></em> is not one

of the accepted defined values.</p><p><code class="constant">GL_INVALID_ENUM</code> is generated if

<em class="parameter"><code>param</code></em> should have a defined constant value (based

on the value of <em class="parameter"><code>pname</code></em>) and does not.</p></div><div class="refsect1" title="See Also"><a id="seealso"></a><h2>See Also</h2><p><a class="citerefentry" href="glActiveTexture"><span class="citerefentry"><span class="refentrytitle">glActiveTexture</span></span></a>, <a class="citerefentry" href="glBindTexture"><span class="citerefentry"><span class="refentrytitle">glBindTexture</span></span></a>, <a class="citerefentry" href="glCopyTexImage2D"><span class="citerefentry"><span class="refentrytitle">glCopyTexImage2D</span></span></a>, <a class="citerefentry" href="glCopyTexSubImage2D"><span class="citerefentry"><span class="refentrytitle">glCopyTexSubImage2D</span></span></a>, <a class="citerefentry" href="glEnable"><span class="citerefentry"><span class="refentrytitle">glEnable</span></span></a>, <a class="citerefentry" href="glPixelStorei"><span class="citerefentry"><span class="refentrytitle">glPixelStorei</span></span></a>, <a class="citerefentry" href="glTexEnv"><span class="citerefentry"><span class="refentrytitle">glTexEnv</span></span></a>, <a class="citerefentry" href="glTexImage2D"><span class="citerefentry"><span class="refentrytitle">glTexImage2D</span></span></a>, <a class="citerefentry" href="glTexSubImage2D"><span class="citerefentry"><span class="refentrytitle">glTexSubImage2D</span></span></a></p></div><div class="refsect1" title="Copyright"><a id="copyright"></a><h2>Copyright</h2><p>Copyright © 2003-2004 Silicon

Graphics, Inc. This document is licensed under the SGI Free Software B

</p></div></div>