mirror of
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787 lines
38 KiB
XML
787 lines
38 KiB
XML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
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"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
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<refentry id="glTexGen">
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<refmeta>
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<refmetainfo>
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<copyright>
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<year>1991-2006</year>
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<holder>Silicon Graphics, Inc.</holder>
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</copyright>
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</refmetainfo>
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<refentrytitle>glTexGen</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glTexGen</refname>
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<refpurpose>control the generation of texture coordinates</refpurpose>
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</refnamediv>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGeni</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>GLint <parameter>param</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGenf</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>GLfloat <parameter>param</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGend</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>GLdouble <parameter>param</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<!-- eqn: ignoring delim $$ -->
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<refsect1 id="parameters"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>coord</parameter></term>
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<listitem>
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<para>
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Specifies a texture coordinate.
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Must be one of <constant>GL_S</constant>, <constant>GL_T</constant>, <constant>GL_R</constant>, or <constant>GL_Q</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>pname</parameter></term>
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<listitem>
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<para>
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Specifies the symbolic name of the texture-coordinate generation function.
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Must be <constant>GL_TEXTURE_GEN_MODE</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>param</parameter></term>
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<listitem>
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<para>
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Specifies a single-valued texture generation parameter,
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one of <constant>GL_OBJECT_LINEAR</constant>, <constant>GL_EYE_LINEAR</constant>, <constant>GL_SPHERE_MAP</constant>,
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<constant>GL_NORMAL_MAP</constant>, or <constant>GL_REFLECTION_MAP</constant>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsynopsisdiv><title>C Specification</title>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGeniv</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>const GLint * <parameter>params</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGenfv</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>const GLfloat * <parameter>params</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>void <function>glTexGendv</function></funcdef>
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<paramdef>GLenum <parameter>coord</parameter></paramdef>
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<paramdef>GLenum <parameter>pname</parameter></paramdef>
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<paramdef>const GLdouble * <parameter>params</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1 id="parameters2"><title>Parameters</title>
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<variablelist>
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<varlistentry>
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<term><parameter>coord</parameter></term>
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<listitem>
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<para>
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Specifies a texture coordinate.
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Must be one of <constant>GL_S</constant>, <constant>GL_T</constant>, <constant>GL_R</constant>, or <constant>GL_Q</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>pname</parameter></term>
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<listitem>
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<para>
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Specifies the symbolic name of the texture-coordinate generation function
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or function parameters.
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Must be
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<constant>GL_TEXTURE_GEN_MODE</constant>,
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<constant>GL_OBJECT_PLANE</constant>, or
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<constant>GL_EYE_PLANE</constant>.
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>params</parameter></term>
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<listitem>
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<para>
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Specifies a pointer to an array of texture generation parameters.
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If <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
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then the array must contain a single symbolic constant,
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one of
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<constant>GL_OBJECT_LINEAR</constant>,
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<constant>GL_EYE_LINEAR</constant>,
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<constant>GL_SPHERE_MAP</constant>,
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<constant>GL_NORMAL_MAP</constant>, or
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<constant>GL_REFLECTION_MAP</constant>.
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Otherwise,
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<parameter>params</parameter> holds the coefficients for the texture-coordinate generation function
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specified by <parameter>pname</parameter>.
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1 id="description"><title>Description</title>
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<para>
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<function>glTexGen</function> selects a texture-coordinate generation function
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or supplies coefficients for one of the functions.
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<parameter>coord</parameter> names one of the (<emphasis>s</emphasis>, <emphasis>t</emphasis>, <emphasis>r</emphasis>, <emphasis>q</emphasis>) texture
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coordinates; it must be one of the symbols
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<constant>GL_S</constant>,
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<constant>GL_T</constant>,
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<constant>GL_R</constant>, or
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<constant>GL_Q</constant>.
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<parameter>pname</parameter> must be one of three symbolic constants:
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<constant>GL_TEXTURE_GEN_MODE</constant>,
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<constant>GL_OBJECT_PLANE</constant>, or
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<constant>GL_EYE_PLANE</constant>.
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If <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
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then <parameter>params</parameter> chooses a mode,
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one of
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<constant>GL_OBJECT_LINEAR</constant>,
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<constant>GL_EYE_LINEAR</constant>,
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<constant>GL_SPHERE_MAP</constant>,
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<constant>GL_NORMAL_MAP</constant>, or
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<constant>GL_REFLECTION_MAP</constant>.
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If <parameter>pname</parameter> is either <constant>GL_OBJECT_PLANE</constant> or <constant>GL_EYE_PLANE</constant>,
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<parameter>params</parameter> contains coefficients for the corresponding
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texture generation function.
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</para>
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<para>
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If the texture generation function is <constant>GL_OBJECT_LINEAR</constant>,
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the function
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</para>
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<para>
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<inlineequation><mml:math>
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<!-- eqn: g = p sub 1 * x sub o + p sub 2 * y sub o + p sub 3 * z sub o + p sub 4 * w sub o:-->
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<mml:mrow>
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<mml:mi mathvariant="italic">g</mml:mi>
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<mml:mo>=</mml:mo>
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<mml:mrow>
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>1</mml:mn>
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</mml:msub>
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<mml:mo>×</mml:mo>
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<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:mrow>
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<mml:mo>+</mml:mo>
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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<mml:mo>×</mml:mo>
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<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:mrow>
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<mml:mo>+</mml:mo>
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>3</mml:mn>
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</mml:msub>
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<mml:mo>×</mml:mo>
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<mml:msub><mml:mi mathvariant="italic">z</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:mrow>
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<mml:mo>+</mml:mo>
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<mml:mrow>
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>4</mml:mn>
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</mml:msub>
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<mml:mo>×</mml:mo>
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<mml:msub><mml:mi mathvariant="italic">w</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:mrow>
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</mml:mrow>
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</mml:mrow>
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</mml:math></inlineequation>
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</para>
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<para>
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is used, where
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<inlineequation><mml:math><mml:mi mathvariant="italic">g</mml:mi></mml:math></inlineequation>
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is the value computed for the coordinate named in <parameter>coord</parameter>,
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<inlineequation><mml:math>
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<!-- eqn: p sub 1:-->
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>1</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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<!-- eqn: p sub 2:-->
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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<!-- eqn: p sub 3:-->
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>3</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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and
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<inlineequation><mml:math>
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<!-- eqn: p sub 4:-->
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>4</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>
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are the four values supplied in <parameter>params</parameter>, and
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<inlineequation><mml:math>
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<!-- eqn: x sub o:-->
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<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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<!-- eqn: y sub o:-->
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<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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<!-- eqn: z sub o:-->
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<mml:msub><mml:mi mathvariant="italic">z</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:math></inlineequation>,
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and
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<inlineequation><mml:math>
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<!-- eqn: w sub o:-->
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<mml:msub><mml:mi mathvariant="italic">w</mml:mi>
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<mml:mi mathvariant="italic">o</mml:mi>
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</mml:msub>
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</mml:math></inlineequation>
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are the object coordinates of the vertex.
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This function can be used, for example, to texture-map terrain using sea level
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as a reference plane
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(defined by
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<inlineequation><mml:math>
|
||
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<!-- eqn: p sub 1:-->
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||
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>1</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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||
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<!-- eqn: p sub 2:-->
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>2</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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<inlineequation><mml:math>
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||
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<!-- eqn: p sub 3:-->
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||
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>3</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>,
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and
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<inlineequation><mml:math>
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||
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<!-- eqn: p sub 4:-->
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||
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<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
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<mml:mn>4</mml:mn>
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</mml:msub>
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</mml:math></inlineequation>).
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The altitude of a terrain vertex is computed by the <constant>GL_OBJECT_LINEAR</constant>
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coordinate generation function as its distance from sea level;
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that altitude can then be used to index the texture image to map white snow
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onto peaks and green grass onto foothills.
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</para>
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<para>
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||
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If the texture generation function is <constant>GL_EYE_LINEAR</constant>, the function
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</para>
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||
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<para>
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||
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<informalequation><mml:math>
|
||
|
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<!-- eqn: g = {p sub 1} sup prime * x sub e + {p sub 2} sup prime * y sub e + {p sub 3} sup prime * z sub e + {p sub 4} sup prime * w sub e:-->
|
||
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<mml:mrow>
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||
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|
<mml:mi mathvariant="italic">g</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>×</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>×</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>3</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>×</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">z</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>4</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>×</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">w</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
is used, where
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<informalequation><mml:math>
|
||
|
|
<!-- eqn: left ( {p sub 1} sup prime {p sub 2} sup prime {p sub 3} sup prime {p sub 4} sup prime right ) = left ( p sub 1 p sub 2 p sub 3 p sub 4 right ) M sup -1:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>3</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>4</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>3</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>4</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mi mathvariant="italic">M</mml:mi>
|
||
|
|
<mml:mn>-1</mml:mn>
|
||
|
|
</mml:msup>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></informalequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: x sub e:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: y sub e:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: z sub e:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">z</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: w sub e:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">w</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">e</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
are the eye coordinates of the vertex,
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: p sub 1:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: p sub 2:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: p sub 3:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>3</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>,
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: p sub 4:-->
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">p</mml:mi>
|
||
|
|
<mml:mn>4</mml:mn>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
are the values supplied in <parameter>params</parameter>, and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">M</mml:mi></mml:math></inlineequation>
|
||
|
|
is the modelview matrix when <function>glTexGen</function> is invoked.
|
||
|
|
If
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">M</mml:mi></mml:math></inlineequation>
|
||
|
|
is poorly conditioned or singular,
|
||
|
|
texture coordinates generated by the resulting function may be inaccurate
|
||
|
|
or undefined.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
Note that the values in <parameter>params</parameter> 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.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
If <parameter>pname</parameter> is <constant>GL_SPHERE_MAP</constant> and <parameter>coord</parameter> is either
|
||
|
|
<constant>GL_S</constant> or
|
||
|
|
<constant>GL_T</constant>,
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
|
||
|
|
texture coordinates are generated as follows.
|
||
|
|
Let <emphasis>u</emphasis> be the unit vector pointing from the origin to the polygon vertex
|
||
|
|
(in eye coordinates).
|
||
|
|
Let <emphasis>n</emphasis> sup prime be the current normal,
|
||
|
|
after transformation to eye coordinates.
|
||
|
|
Let
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: f = ( f sub x f sub y f sub z ) sup T:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">z</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mi mathvariant="italic">T</mml:mi>
|
||
|
|
</mml:msup>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
be the reflection vector such that
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: f = u - 2 n sup prime {n sup prime} sup T u:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">u</mml:mi>
|
||
|
|
<mml:mo>-</mml:mo>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msup><mml:mi mathvariant="italic">n</mml:mi>
|
||
|
|
<mml:mo>″</mml:mo>
|
||
|
|
</mml:msup>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mi mathvariant="italic">T</mml:mi>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:mi mathvariant="italic">u</mml:mi>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
Finally, let
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: m = 2 sqrt ({f sub x} sup 2 + {f sub y} sup 2 + (f sub z + 1) sup 2):-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">m</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
<mml:mo>⁢</mml:mo>
|
||
|
|
<mml:msqrt>
|
||
|
|
<mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="" close="">
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msup>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:msup><mml:mfenced open="(" close=")">
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">z</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mo>+</mml:mo>
|
||
|
|
<mml:mn>1</mml:mn>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
<mml:mn>2</mml:mn>
|
||
|
|
</mml:msup>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mfenced>
|
||
|
|
</mml:msqrt>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:mrow>
|
||
|
|
</mml:math></inlineequation>.
|
||
|
|
Then the values assigned to the
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
|
||
|
|
texture coordinates are
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: s = f sub x over m + 1 over 2:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">s</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfrac>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">x</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mi mathvariant="italic">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:mrow>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<inlineequation><mml:math>
|
||
|
|
<!-- eqn: t = f sub y over m + 1 over 2:-->
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mi mathvariant="italic">t</mml:mi>
|
||
|
|
<mml:mo>=</mml:mo>
|
||
|
|
<mml:mrow>
|
||
|
|
<mml:mfrac>
|
||
|
|
<mml:msub><mml:mi mathvariant="italic">f</mml:mi>
|
||
|
|
<mml:mi mathvariant="italic">y</mml:mi>
|
||
|
|
</mml:msub>
|
||
|
|
<mml:mi mathvariant="italic">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:mrow>
|
||
|
|
</mml:math></inlineequation>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
To enable or disable a texture-coordinate generation function, call
|
||
|
|
<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
|
||
|
|
with one of the symbolic texture-coordinate names
|
||
|
|
(<constant>GL_TEXTURE_GEN_S</constant>,
|
||
|
|
<constant>GL_TEXTURE_GEN_T</constant>,
|
||
|
|
<constant>GL_TEXTURE_GEN_R</constant>, or
|
||
|
|
<constant>GL_TEXTURE_GEN_Q</constant>) 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 <constant>GL_EYE_LINEAR</constant> and are disabled.
|
||
|
|
Both
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
|
||
|
|
plane equations are (1, 0, 0, 0),
|
||
|
|
both
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">t</mml:mi></mml:math></inlineequation>
|
||
|
|
plane equations are (0, 1, 0, 0),
|
||
|
|
and all
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">r</mml:mi></mml:math></inlineequation>
|
||
|
|
and
|
||
|
|
<inlineequation><mml:math><mml:mi mathvariant="italic">q</mml:mi></mml:math></inlineequation>
|
||
|
|
plane equations are (0, 0, 0, 0).
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
When the <code>ARB_multitexture</code> extension is supported, <function>glTexGen</function> set the
|
||
|
|
texture generation parameters for the currently active texture unit,
|
||
|
|
selected with <citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="errors"><title>Errors</title>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_ENUM</constant> is generated when <parameter>coord</parameter> or <parameter>pname</parameter> is not an
|
||
|
|
accepted defined value,
|
||
|
|
or when <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant> and <parameter>params</parameter> is not an
|
||
|
|
accepted defined value.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_ENUM</constant> is generated when <parameter>pname</parameter> is <constant>GL_TEXTURE_GEN_MODE</constant>,
|
||
|
|
<parameter>params</parameter> is <constant>GL_SPHERE_MAP</constant>,
|
||
|
|
and <parameter>coord</parameter> is either <constant>GL_R</constant> or <constant>GL_Q</constant>.
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glTexGen</function>
|
||
|
|
is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
|
||
|
|
and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="associatedgets"><title>Associated Gets</title>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glGetTexGen</refentrytitle></citerefentry>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_S</constant>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_T</constant>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_R</constant>
|
||
|
|
</para>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_TEXTURE_GEN_Q</constant>
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
<refsect1 id="seealso"><title>See Also</title>
|
||
|
|
<para>
|
||
|
|
<citerefentry><refentrytitle>glActiveTexture</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyPixels</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyTexImage2D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyTexSubImage1D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyTexSubImage2D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glCopyTexSubImage3D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glTexEnv</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glTexImage1D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glTexImage2D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glTexImage3D</refentrytitle></citerefentry>,
|
||
|
|
<citerefentry><refentrytitle>glTexParameter</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
|
||
|
|
Silicon Graphics, Inc. This document is licensed under the SGI
|
||
|
|
Free Software B License. For details, see
|
||
|
|
<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
|
||
|
|
</para>
|
||
|
|
</refsect1>
|
||
|
|
</refentry>
|