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<?xml version="1.0" encoding="ISO-8859-1"?>
<!DOCTYPE html
PUBLIC "-//W3C//DTD XHTML 1.1 plus MathML 2.0//EN" "http://www.w3.org/TR/MathML2/dtd/xhtml-math11-f.dtd">
<html
xmlns="http://www.w3.org/1999/xhtml"
xmlns:mml="http://www.w3.org/1998/Math/MathML"
><head><title>glTexGen</title><link rel="stylesheet" href="style.css" type="text/css"/><meta name="generator" content="DocBook XSL Stylesheets V1.59.1"/><link rel="home" href="index.xml" title="PyOpenGL 2.0.1.07 Man Pages"/><link rel="up" href="reference-GL.xml" title="GL"/><link rel="previous" href="glTexEnv.3G.xml" title="glTexEnv"/><link rel="next" href="glTexImage1D.3G.xml" title="glTexImage1D"/></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">glTexGen</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="glTexEnv.3G.xml">Prev</a></td><th width="60%" align="center">GL</th><td width="20%" align="right"><a accesskey="n" href="glTexImage1D.3G.xml">Next</a></td></tr></table><hr/></div><div class="refentry" lang="en"><a name="glTexGen.3G"/><div class="titlepage"/><div class="refnamediv"><a name="glTexGen.3G-name"/><h2>Name</h2><p>glTexGend, glTexGenf, glTexGeni, glTexGendv, glTexGenfv, glTexGeniv — control the generation of texture coordinates</p></div><div class="refsynopsisdiv"><a name="glTexGen.3G-c_spec"/><h2>C Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code>void<tt>glTexGend</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, GLdouble<i><tt>param</tt></i>);</code></td></tr><tr><td valign="top"><code>void<tt>glTexGenf</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, GLfloat<i><tt>param</tt></i>);</code></td></tr><tr><td valign="top"><code>void<tt>glTexGeni</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, GLint<i><tt>param</tt></i>);</code></td></tr></table></div><div class="refsynopsisdiv"><a name="glTexGen.3G-python_spec"/><h2>Python Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code><tt>glTexGend</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>param</tt></i>) →<tt>None</tt></code></td></tr><tr><td valign="top"><code><tt>glTexGenf</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>param</tt></i>) →<tt>None</tt></code></td></tr><tr><td valign="top"><code><tt>glTexGeni</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>param</tt></i>) →<tt>None</tt></code></td></tr></table></div><div class="refsect1" lang="en"><a name="glTexGen.3G-parameters"/><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><i><tt>coord</tt></i></span></dt><dd>
Specifies a texture coordinate. Must be one of <tt>GL_S</tt>, <tt>GL_T</tt>,
<tt>GL_R</tt>, or <tt>GL_Q</tt>.
</dd><dt><span class="term"><i><tt>pname</tt></i></span></dt><dd>
Specifies the symbolic name of the texture-coordinate generation function. Must be
<tt>GL_TEXTURE_GEN_MODE</tt>.
</dd><dt><span class="term"><i><tt>param</tt></i></span></dt><dd>
Specifies a single-valued texture generation parameter, one of <tt>GL_OBJECT_LINEAR</tt>,
<tt>GL_EYE_LINEAR</tt>, or <tt>GL_SPHERE_MAP</tt>.
</dd></dl></div></div><div class="refsynopsisdiv"><a name="glTexGen.3G-c_spec-v"/><h2>C Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code>void<tt>glTexGendv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, constGLdouble*<i><tt>params</tt></i>);</code></td></tr><tr><td valign="top"><code>void<tt>glTexGenfv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, constGLfloat*<i><tt>params</tt></i>);</code></td></tr><tr><td valign="top"><code>void<tt>glTexGeniv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code>GLenum<i><tt>coord</tt></i>, GLenum<i><tt>pname</tt></i>, constGLint*<i><tt>params</tt></i>);</code></td></tr></table></div><div class="refsynopsisdiv"><a name="glTexGen.3G-python_spec-v"/><h2>Python Specification</h2><table class="funcprototype" border="0" cellpadding="0" cellspacing="0"><tr><td valign="top"><code><tt>glTexGendv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>params</tt></i>) →<tt>None</tt></code></td></tr><tr><td valign="top"><code><tt>glTexGenfv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>params</tt></i>) →<tt>None</tt></code></td></tr><tr><td valign="top"><code><tt>glTexGeniv</tt></code></td><td valign="top"><code>(</code></td><td valign="top"><code><i><tt>coord</tt></i>, <i><tt>pname</tt></i>, <i><tt>params</tt></i>) →<tt>None</tt></code></td></tr></table></div><div class="refsect1" lang="en"><a name="glTexGen.3G-parameters-v"/><h2>Parameters</h2><div class="variablelist"><dl><dt><span class="term"><i><tt>coord</tt></i></span></dt><dd>
Specifies a texture coordinate. Must be one of <tt>GL_S</tt>, <tt>GL_T</tt>,
<tt>GL_R</tt>, or <tt>GL_Q</tt>.
</dd><dt><span class="term"><i><tt>pname</tt></i></span></dt><dd>
Specifies the symbolic name of the texture-coordinate generation function or function parameters. Must be
<tt>GL_TEXTURE_GEN_MODE</tt>, <tt>GL_OBJECT_PLANE</tt>, or
<tt>GL_EYE_PLANE</tt>.
</dd><dt><span class="term"><i><tt>params</tt></i></span></dt><dd>
Specifies a pointer to an array of texture generation parameters. If <i><tt>pname</tt></i> is
<tt>GL_TEXTURE_GEN_MODE</tt>, then the array must contain a single symbolic constant, one of
<tt>GL_OBJECT_LINEAR</tt>, <tt>GL_EYE_LINEAR</tt>, or
<tt>GL_SPHERE_MAP</tt>. Otherwise, <i><tt>params</tt></i> holds the coefficients for the
texture-coordinate generation function specified by <i><tt>pname</tt></i>.
</dd></dl></div></div><div class="refsect1" lang="en"><a name="glTexGen.3G-description"/><h2>Description</h2><p>
<tt>glTexGen</tt> selects a texture-coordinate generation function or supplies
coefficients for one of the functions. <i><tt>coord</tt></i> names one of the (<i><tt>s</tt></i>,
<i><tt>t</tt></i>, <i><tt>r</tt></i>, <i><tt>q</tt></i>) texture coordinates; it must be one of
the symbols <tt>GL_S</tt>, <tt>GL_T</tt>, <tt>GL_R</tt>, or
<tt>GL_Q</tt>. <i><tt>pname</tt></i> must be one of three symbolic constants:
<tt>GL_TEXTURE_GEN_MODE</tt>, <tt>GL_OBJECT_PLANE</tt>, or <tt>GL_EYE_PLANE</tt>.
If <i><tt>pname</tt></i> is <tt>GL_TEXTURE_GEN_MODE</tt>, then <i><tt>params</tt></i> chooses
a mode, one of <tt>GL_OBJECT_LINEAR</tt>, <tt>GL_EYE_LINEAR</tt>, or
<tt>GL_SPHERE_MAP</tt>. If <i><tt>pname</tt></i> is either <tt>GL_OBJECT_PLANE</tt> or
<tt>GL_EYE_PLANE</tt>, <i><tt>params</tt></i> contains coefficients for the corresponding texture
generation function.
</p><p>
If the texture generation function is <tt>GL_OBJECT_LINEAR</tt>, the function
</p><p>
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terrain using sea level as a reference plane (defined by <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
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coordinate generation function as its distance from sea level; that altitude can then be used to index the texture
image to map white snow onto peaks and green grass onto foothills.
</p><p>
If the texture generation function is <tt>GL_EYE_LINEAR</tt>, the function
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<mml:mn>3</mml:mn>
</mml:msub>
</mml:math>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:msub>
<mml:mi>p</mml:mi>
<mml:mn>4</mml:mn>
</mml:msub>
</mml:math> are the values supplied in <i><tt>params</tt></i>, and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>M</mml:mi>
</mml:math> is the modelview matrix when <tt>glTexGen</tt> is invoked. If
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>M</mml:mi>
</mml:math> is poorly conditioned or singular, texture coordinates generated by the resulting function may be
inaccurate or undefined.
</p><p>
Note that the values in <i><tt>params</tt></i> define a reference plane in eye coordinates. The modelview matrix
that is applied to them may not be the same one in effect when the polygon vertices are transformed. This function
establishes a field of texture coordinates that can produce dynamic contour lines on moving objects.
</p><p>
If <i><tt>pname</tt></i> is <tt>GL_SPHERE_MAP</tt> and <i><tt>coord</tt></i> is either
<tt>GL_S</tt> or <tt>GL_T</tt>, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>s</mml:mi>
</mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>t</mml:mi>
</mml:math> texture coordinates are generated as follows. Let <i><tt>u</tt></i> be the unit vector
pointing from the origin to the polygon vertex (in eye coordinates). Let <i><tt>n</tt></i> sup prime be the
current normal, after transformation to eye coordinates. Let
</p><p>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>f</mml:mi>
<mml:mo>=</mml:mo>
<mml:mo>(</mml:mo>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>y</mml:mi>
</mml:msub>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>z</mml:mi>
</mml:msub>
<mml:msup>
<mml:mo>)</mml:mo>
<mml:mi>T</mml:mi>
</mml:msup>
</mml:mrow>
</mml:math> be the reflection vector such that
</p><p>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>f</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi>u</mml:mi>
<mml:mo>-</mml:mo>
<mml:mn>2</mml:mn>
<mml:msup>
<mml:mi>n</mml:mi>
<mml:mo>'</mml:mo>
</mml:msup>
<mml:msup>
<mml:msup>
<mml:mi>n</mml:mi>
<mml:mo>'</mml:mo>
</mml:msup>
<mml:mi>T</mml:mi>
</mml:msup>
<mml:mi>u</mml:mi>
</mml:mrow>
</mml:math>
</p><p>
Finally, let <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>m</mml:mi>
<mml:mo>=</mml:mo>
<mml:mn>2</mml:mn>
<mml:msqrt>
<mml:mrow>
<mml:msup>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo>+</mml:mo>
<mml:msup>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>y</mml:mi>
</mml:msub>
<mml:mrow>
<mml:mn>2</mml:mn>
</mml:mrow>
</mml:msup>
<mml:mo>+</mml:mo>
<mml:mo>(</mml:mo>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>z</mml:mi>
</mml:msub>
<mml:mo>+</mml:mo>
<mml:mn>1</mml:mn>
<mml:msup>
<mml:mo>)</mml:mo>
<mml:mn>2</mml:mn>
</mml:msup>
</mml:mrow>
</mml:msqrt>
</mml:mrow>
</mml:math>. Then the values assigned to the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>s</mml:mi>
</mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>t</mml:mi>
</mml:math> texture coordinates are
</p><p>
<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>s</mml:mi>
<mml:mo>=</mml:mo>
<mml:mfrac>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>x</mml:mi>
</mml:msub>
<mml:mi>m</mml:mi>
</mml:mfrac>
<mml:mo>+</mml:mo>
<mml:mfrac>
<mml:mn>1</mml:mn>
<mml:mn>2</mml:mn>
</mml:mfrac>
</mml:mrow>
</mml:math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mrow>
<mml:mi>t</mml:mi>
<mml:mo>=</mml:mo>
<mml:mfrac>
<mml:msub>
<mml:mi>f</mml:mi>
<mml:mi>y</mml:mi>
</mml:msub>
<mml:mi>m</mml:mi>
</mml:mfrac>
<mml:mo>+</mml:mo>
<mml:mfrac>
<mml:mn>1</mml:mn>
<mml:mn>2</mml:mn>
</mml:mfrac>
</mml:mrow>
</mml:math>
</p><p>
To enable or disable a texture-coordinate generation function, call <a href="glEnable.3G.xml"><tt>glEnable</tt></a>
or <a href="glEnable.3G.xml"><tt>glDisable</tt></a> with one of the symbolic texture-coordinate names
(<tt>GL_TEXTURE_GEN_S</tt>, <tt>GL_TEXTURE_GEN_T</tt>, <tt>GL_TEXTURE_GEN_R</tt>,
or <tt>GL_TEXTURE_GEN_Q</tt>) as the argument. When enabled, the specified texture coordinate is computed
according to the generating function associated with that coordinate. When disabled, subsequent vertices take the
specified texture coordinate from the current set of texture coordinates. Initially, all texture generation functions
are set to <tt>GL_EYE_LINEAR</tt> and are disabled. Both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>s</mml:mi>
</mml:math> plane equations are (1, 0, 0, 0), both <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>t</mml:mi>
</mml:math> plane equations are (0, 1, 0, 0), and all <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>r</mml:mi>
</mml:math> and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll">
<mml:mi>q</mml:mi>
</mml:math> plane equations are (0, 0, 0, 0).
</p><p>
When the <tt>GL_ARB_multitexture</tt> extension is supported, <tt>glTexGen</tt> set the texture generation parameters for the currently active texture unit,
selected with <a href="glActiveTextureARB.3G.xml"><tt>glActiveTextureARB</tt></a>.
</p></div><div class="refsect1" lang="en"><a name="glTexGen.3G-errors"/><h2>Errors</h2><p>
<tt>GL_INVALID_ENUM</tt> is generated when <i><tt>coord</tt></i> or <i><tt>pname</tt></i> is
not an accepted defined value, or when <i><tt>pname</tt></i> is <tt>GL_TEXTURE_GEN_MODE</tt> and
<i><tt>params</tt></i> is not an accepted defined value.
</p><p>
<tt>GL_INVALID_ENUM</tt> is generated when <i><tt>pname</tt></i> is
<tt>GL_TEXTURE_GEN_MODE</tt>, <i><tt>params</tt></i> is <tt>GL_SPHERE_MAP</tt>, and
<i><tt>coord</tt></i> is either <tt>GL_R</tt> or <tt>GL_Q</tt>.
</p><p>
<tt>GL_INVALID_OPERATION</tt> is generated if <tt>glTexGen</tt> is executed
between the execution of <a href="glBegin.3G.xml"><tt>glBegin</tt></a> and the corresponding execution of <a href="glBegin.3G.xml"><tt>glEnd</tt></a>.
</p></div><div class="refsect1" lang="en"><a name="glTexGen.3G-associated_gets"/><h2>Associated Gets</h2><p>
<tt>glGetTexGen</tt>
</p><p>
<a href="glIsEnabled.3G.xml"><tt>glIsEnabled</tt></a> with argument <tt>GL_TEXTURE_GEN_S</tt>
</p><p>
<a href="glIsEnabled.3G.xml"><tt>glIsEnabled</tt></a> with argument <tt>GL_TEXTURE_GEN_T</tt>
</p><p>
<a href="glIsEnabled.3G.xml"><tt>glIsEnabled</tt></a> with argument <tt>GL_TEXTURE_GEN_R</tt>
</p><p>
<a href="glIsEnabled.3G.xml"><tt>glIsEnabled</tt></a> with argument <tt>GL_TEXTURE_GEN_Q</tt>
</p></div><div class="refsect1" lang="en"><a name="glTexGen.3G-see_also"/><h2>See Also</h2><p>
<span class="simplelist"><a href="glActiveTextureARB.3G.xml">glActiveTextureARB</a>, <a href="glCopyPixels.3G.xml">glCopyPixels</a>, <a href="glCopyTexImage2D.3G.xml">glCopyTexImage2D</a>, <a href="glCopyTexSubImage1D.3G.xml">glCopyTexSubImage1D</a>, <a href="glCopyTexSubImage2D.3G.xml">glCopyTexSubImage2D</a>, <a href="glCopyTexSubImage3D.3G.xml">glCopyTexSubImage3D</a>, <a href="glTexEnv.3G.xml">glTexEnv</a>, <a href="glTexImage1D.3G.xml">glTexImage1D</a>, <a href="glTexImage2D.3G.xml">glTexImage2D</a>, <a href="glTexImage3D.3G.xml">glTexImage3D</a>, <a href="glTexParameter.3G.xml">glTexParameter</a>, <a href="glTexSubImage1D.3G.xml">glTexSubImage1D</a>, <a href="glTexSubImage2D.3G.xml">glTexSubImage2D</a>, <a href="glTexSubImage3D.3G.xml">glTexSubImage3D</a></span>
</p></div></div><div class="navfooter"><hr/><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="glTexEnv.3G.xml">Prev</a></td><td width="20%" align="center"><a accesskey="u" href="reference-GL.xml">Up</a></td><td width="40%" align="right"><a accesskey="n" href="glTexImage1D.3G.xml">Next</a></td></tr><tr><td width="40%" align="left" valign="top">glTexEnv</td><td width="20%" align="center"><a accesskey="h" href="index.xml">Home</a></td><td width="40%" align="right" valign="top">glTexImage1D</td></tr></table></div></body></html>
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