[clinton/guile-figl.git] / upstream-doc / man2 / glEvalCoord.xml

<?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="glEvalCoord">
    <refmeta>
        <refmetainfo>
            <copyright>
                <year>1991-2006</year>
                <holder>Silicon Graphics, Inc.</holder>
            </copyright>
        </refmetainfo>
        <refentrytitle>glEvalCoord</refentrytitle>
        <manvolnum>3G</manvolnum>
    </refmeta>
    <refnamediv>
        <refname>glEvalCoord</refname>
        <refpurpose>evaluate enabled one- and two-dimensional maps</refpurpose>
    </refnamediv>
    <!-- eqn: ignoring delim $$ -->
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord1f</function></funcdef>
                <paramdef>GLfloat <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord1d</function></funcdef>
                <paramdef>GLdouble <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord2f</function></funcdef>
                <paramdef>GLfloat <parameter>u</parameter></paramdef>
                <paramdef>GLfloat <parameter>v</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord2d</function></funcdef>
                <paramdef>GLdouble <parameter>u</parameter></paramdef>
                <paramdef>GLdouble <parameter>v</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>u</parameter></term>
            <listitem>
                <para>
                    Specifies a value that is the domain coordinate 
                    <inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
                    to the basis function
                    defined in a previous <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> command.
                </para>
            </listitem>
        </varlistentry>
        <varlistentry>
            <term><parameter>v</parameter></term>
            <listitem>
                <para>
                    Specifies a value that is the domain coordinate 
                    <inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>
                    to the basis function
                    defined in a previous <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> command.
                    This argument is not present in a <function>glEvalCoord1</function> command.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsynopsisdiv><title>C Specification</title>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord1fv</function></funcdef>
                <paramdef>const GLfloat * <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord1dv</function></funcdef>
                <paramdef>const GLdouble * <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord2fv</function></funcdef>
                <paramdef>const GLfloat * <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
        <funcsynopsis>
            <funcprototype>
                <funcdef>void <function>glEvalCoord2dv</function></funcdef>
                <paramdef>const GLdouble * <parameter>u</parameter></paramdef>
            </funcprototype>
        </funcsynopsis>
    </refsynopsisdiv>
    <refsect1 id="parameters2"><title>Parameters</title>
        <variablelist>
        <varlistentry>
            <term><parameter>u</parameter></term>
            <listitem>
                <para>
                    Specifies a pointer to an array containing
                    either one or two domain coordinates.
                    The first coordinate is 
                    <inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>.
                    The second coordinate is 
                    <inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>,
                    which is present only in <function>glEvalCoord2</function> versions.
                </para>
            </listitem>
        </varlistentry>
        </variablelist>
    </refsect1>
    <refsect1 id="description"><title>Description</title>
        <para>
            <function>glEvalCoord1</function> evaluates enabled one-dimensional maps at argument
            <parameter>u</parameter>.
            <function>glEvalCoord2</function> does the same for two-dimensional maps using
            two domain values,
            <parameter>u</parameter> and <parameter>v</parameter>.
            To define a map, call <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>; to enable and
            disable it, call <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>.
        </para>
        <para>
            When one of the <function>glEvalCoord</function> commands is issued,
            all currently enabled maps of the indicated dimension are evaluated.
            Then,
            for each enabled map,
            it is as if the corresponding GL command had been issued with the
            computed value.
            That is,
            if <constant>GL_MAP1_INDEX</constant> or
            <constant>GL_MAP2_INDEX</constant> is enabled,
            a <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry> command is simulated.
            If <constant>GL_MAP1_COLOR_4</constant> or
            <constant>GL_MAP2_COLOR_4</constant> is enabled,
            a <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry> command is simulated.
            If <constant>GL_MAP1_NORMAL</constant> or <constant>GL_MAP2_NORMAL</constant> is enabled,
            a normal vector is produced,
            and if any of
            <constant>GL_MAP1_TEXTURE_COORD_1</constant>,
            <constant>GL_MAP1_TEXTURE_COORD_2</constant>,
            <constant>GL_MAP1_TEXTURE_COORD_3</constant>,
            <constant>GL_MAP1_TEXTURE_COORD_4</constant>,
            <constant>GL_MAP2_TEXTURE_COORD_1</constant>,
            <constant>GL_MAP2_TEXTURE_COORD_2</constant>,
            <constant>GL_MAP2_TEXTURE_COORD_3</constant>, or
            <constant>GL_MAP2_TEXTURE_COORD_4</constant> is enabled, then an appropriate <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> command is simulated.
        </para>
        <para>
            For color,
            color index,
            normal,
            and texture coordinates the GL uses evaluated values instead of current values for those evaluations
            that are enabled,
            and current values otherwise,
            However,
            the evaluated values do not update the current values.
            Thus, if <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry> commands are interspersed with <function>glEvalCoord</function>
            commands, the color,
            normal,
            and texture coordinates associated with the <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry> commands are not
            affected by the values generated by the <function>glEvalCoord</function> commands,
            but only by the most recent
            <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>, and
            <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
        </para>
        <para>
            No commands are issued for maps that are not enabled.
            If more than one texture evaluation is enabled for a particular dimension
            (for example, <constant>GL_MAP2_TEXTURE_COORD_1</constant> and
            <constant>GL_MAP2_TEXTURE_COORD_2</constant>),
            then only the evaluation of the map that produces the larger
            number of coordinates
            (in this case, <constant>GL_MAP2_TEXTURE_COORD_2</constant>)
            is carried out.
            <constant>GL_MAP1_VERTEX_4</constant> overrides <constant>GL_MAP1_VERTEX_3</constant>,
            and
            <constant>GL_MAP2_VERTEX_4</constant> overrides <constant>GL_MAP2_VERTEX_3</constant>,
            in the same manner.
            If neither a three- nor a four-component vertex map is enabled for the
            specified dimension,
            the <function>glEvalCoord</function> command is ignored.
        </para>
        <para>
            If you have enabled automatic normal generation,
            by calling <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> with argument <constant>GL_AUTO_NORMAL</constant>,
            <function>glEvalCoord2</function> generates surface normals analytically,
            regardless of the contents or enabling of the <constant>GL_MAP2_NORMAL</constant> map.
            Let
        </para>
        <para>
            <informalequation><mml:math>
                <!-- eqn: bold m  =  { {partial bold p} over {partial u} }  times    { {partial bold p} over {partial v} }:-->
                <mml:mrow>
                    <mml:mi mathvariant="bold">m</mml:mi>
                    <mml:mo>=</mml:mo>
                    <mml:mrow>
                        <mml:mfenced open="" close="">
                            <mml:mfrac>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mo>&PartialD;</mml:mo>
                                        <mml:mi mathvariant="bold">p</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mo>&PartialD;</mml:mo>
                                        <mml:mi mathvariant="italic">u</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                            </mml:mfrac>
                        </mml:mfenced>
                        <mml:mo>&times;</mml:mo>
                        <mml:mfenced open="" close="">
                            <mml:mfrac>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mo>&PartialD;</mml:mo>
                                        <mml:mi mathvariant="bold">p</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                                <mml:mfenced open="" close="">
                                    <mml:mrow>
                                        <mml:mo>&PartialD;</mml:mo>
                                        <mml:mi mathvariant="italic">v</mml:mi>
                                    </mml:mrow>
                                </mml:mfenced>
                            </mml:mfrac>
                        </mml:mfenced>
                    </mml:mrow>
                </mml:mrow>
            </mml:math></informalequation>
        </para>
        <para>
            Then the generated normal 
            <inlineequation><mml:math>
                <!-- eqn: bold n:-->
                <mml:mi mathvariant="bold">n</mml:mi>
            </mml:math></inlineequation>
            is
            <inlineequation><mml:math>
                <!-- eqn: bold n  =  bold m over { || bold m || }:-->
                <mml:mrow>
                    <mml:mi mathvariant="bold">n</mml:mi>
                    <mml:mo>=</mml:mo>
                    <mml:mfrac>
                        <mml:mi mathvariant="bold">m</mml:mi>
                        <mml:mfenced open="" close="">
                            <mml:mfenced open="&DoubleVerticalBar;" close="&DoubleVerticalBar;">
                                <mml:mi mathvariant="bold">m</mml:mi>
                            </mml:mfenced>
                        </mml:mfenced>
                    </mml:mfrac>
                </mml:mrow>
            </mml:math></inlineequation>
        </para>
        <para>
            If automatic normal generation is disabled,
            the corresponding normal map <constant>GL_MAP2_NORMAL</constant>,
            if enabled,
            is used to produce a normal.
            If neither automatic normal generation nor a normal map is enabled,
            no normal is generated for
            <function>glEvalCoord2</function> commands.
        </para>
    </refsect1>
    <refsect1 id="associatedgets"><title>Associated Gets</title>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_3</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_INDEX</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_COLOR_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_NORMAL</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_1</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_2</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_3</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_VERTEX_3</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_VERTEX_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_INDEX</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_COLOR_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_NORMAL</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_1</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_2</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_3</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_4</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_AUTO_NORMAL</constant>
        </para>
        <para>
            <citerefentry><refentrytitle>glGetMap</refentrytitle></citerefentry>
        </para>
    </refsect1>
    <refsect1 id="seealso"><title>See Also</title>
        <para>
            <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glEvalPoint</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glMapGrid</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>glVertex</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>
Commit	Line	Data
7faf1d71 AW	1	<?xml version="1.0" encoding="UTF-8"?>
	2	<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
	3	"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
	4	<refentry id="glEvalCoord">
	5	<refmeta>
	6	<refmetainfo>
	7	<copyright>
	8	<year>1991-2006</year>
	9	<holder>Silicon Graphics, Inc.</holder>
	10	</copyright>
	11	</refmetainfo>
	12	<refentrytitle>glEvalCoord</refentrytitle>
	13	<manvolnum>3G</manvolnum>
	14	</refmeta>
	15	<refnamediv>
	16	<refname>glEvalCoord</refname>
	17	<refpurpose>evaluate enabled one- and two-dimensional maps</refpurpose>
	18	</refnamediv>
	19	<!-- eqn: ignoring delim $$ -->
	20	<refsynopsisdiv><title>C Specification</title>
	21	<funcsynopsis>
	22	<funcprototype>
	23	<funcdef>void <function>glEvalCoord1f</function></funcdef>
	24	<paramdef>GLfloat <parameter>u</parameter></paramdef>
	25	</funcprototype>
	26	</funcsynopsis>
	27	<funcsynopsis>
	28	<funcprototype>
	29	<funcdef>void <function>glEvalCoord1d</function></funcdef>
	30	<paramdef>GLdouble <parameter>u</parameter></paramdef>
	31	</funcprototype>
	32	</funcsynopsis>
	33	<funcsynopsis>
	34	<funcprototype>
	35	<funcdef>void <function>glEvalCoord2f</function></funcdef>
	36	<paramdef>GLfloat <parameter>u</parameter></paramdef>
	37	<paramdef>GLfloat <parameter>v</parameter></paramdef>
	38	</funcprototype>
	39	</funcsynopsis>
	40	<funcsynopsis>
	41	<funcprototype>
	42	<funcdef>void <function>glEvalCoord2d</function></funcdef>
	43	<paramdef>GLdouble <parameter>u</parameter></paramdef>
	44	<paramdef>GLdouble <parameter>v</parameter></paramdef>
	45	</funcprototype>
	46	</funcsynopsis>
	47	</refsynopsisdiv>
	48	<refsect1 id="parameters"><title>Parameters</title>
	49	<variablelist>
	50	<varlistentry>
	51	<term><parameter>u</parameter></term>
	52	<listitem>
	53	<para>
	54	Specifies a value that is the domain coordinate
	55	<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
	56	to the basis function
	57	defined in a previous <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> or <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> command.
	58	</para>
	59	</listitem>
	60	</varlistentry>
	61	<varlistentry>
	62	<term><parameter>v</parameter></term>
	63	<listitem>
	64	<para>
65	Specifies a value that is the domain coordinate
66	<inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>
67	to the basis function
68	defined in a previous <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> command.
69	This argument is not present in a <function>glEvalCoord1</function> command.
70	</para>
71	</listitem>
72	</varlistentry>
73	</variablelist>
74	</refsect1>
75	<refsynopsisdiv><title>C Specification</title>
76	<funcsynopsis>
77	<funcprototype>
78	<funcdef>void <function>glEvalCoord1fv</function></funcdef>
79	<paramdef>const GLfloat * <parameter>u</parameter></paramdef>
80	</funcprototype>
81	</funcsynopsis>
82	<funcsynopsis>
83	<funcprototype>
84	<funcdef>void <function>glEvalCoord1dv</function></funcdef>
85	<paramdef>const GLdouble * <parameter>u</parameter></paramdef>
86	</funcprototype>
87	</funcsynopsis>
88	<funcsynopsis>
89	<funcprototype>
90	<funcdef>void <function>glEvalCoord2fv</function></funcdef>
91	<paramdef>const GLfloat * <parameter>u</parameter></paramdef>
92	</funcprototype>
93	</funcsynopsis>
94	<funcsynopsis>
95	<funcprototype>
96	<funcdef>void <function>glEvalCoord2dv</function></funcdef>
97	<paramdef>const GLdouble * <parameter>u</parameter></paramdef>
98	</funcprototype>
99	</funcsynopsis>
100	</refsynopsisdiv>
101	<refsect1 id="parameters2"><title>Parameters</title>
102	<variablelist>
103	<varlistentry>
104	<term><parameter>u</parameter></term>
105	<listitem>
106	<para>
107	Specifies a pointer to an array containing
108	either one or two domain coordinates.
109	The first coordinate is
110	<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>.
111	The second coordinate is
112	<inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>,
113	which is present only in <function>glEvalCoord2</function> versions.
114	</para>
115	</listitem>
116	</varlistentry>
117	</variablelist>
118	</refsect1>
119	<refsect1 id="description"><title>Description</title>
120	<para>
121	<function>glEvalCoord1</function> evaluates enabled one-dimensional maps at argument
122	<parameter>u</parameter>.
123	<function>glEvalCoord2</function> does the same for two-dimensional maps using
124	two domain values,
125	<parameter>u</parameter> and <parameter>v</parameter>.
126	To define a map, call <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>; to enable and
127	disable it, call <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>.
128	</para>
129	<para>
130	When one of the <function>glEvalCoord</function> commands is issued,
131	all currently enabled maps of the indicated dimension are evaluated.
132	Then,
133	for each enabled map,
134	it is as if the corresponding GL command had been issued with the
135	computed value.
136	That is,
137	if <constant>GL_MAP1_INDEX</constant> or
138	<constant>GL_MAP2_INDEX</constant> is enabled,
139	a <citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry> command is simulated.
140	If <constant>GL_MAP1_COLOR_4</constant> or
141	<constant>GL_MAP2_COLOR_4</constant> is enabled,
142	a <citerefentry><refentrytitle>glColor</refentrytitle></citerefentry> command is simulated.
143	If <constant>GL_MAP1_NORMAL</constant> or <constant>GL_MAP2_NORMAL</constant> is enabled,
144	a normal vector is produced,
145	and if any of
146	<constant>GL_MAP1_TEXTURE_COORD_1</constant>,
147	<constant>GL_MAP1_TEXTURE_COORD_2</constant>,
148	<constant>GL_MAP1_TEXTURE_COORD_3</constant>,
149	<constant>GL_MAP1_TEXTURE_COORD_4</constant>,
150	<constant>GL_MAP2_TEXTURE_COORD_1</constant>,
151	<constant>GL_MAP2_TEXTURE_COORD_2</constant>,
152	<constant>GL_MAP2_TEXTURE_COORD_3</constant>, or
153	<constant>GL_MAP2_TEXTURE_COORD_4</constant> is enabled, then an appropriate <citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> command is simulated.
154	</para>
155	<para>
156	For color,
157	color index,
158	normal,
159	and texture coordinates the GL uses evaluated values instead of current values for those evaluations
160	that are enabled,
161	and current values otherwise,
162	However,
163	the evaluated values do not update the current values.
164	Thus, if <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry> commands are interspersed with <function>glEvalCoord</function>
165	commands, the color,
166	normal,
167	and texture coordinates associated with the <citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry> commands are not
168	affected by the values generated by the <function>glEvalCoord</function> commands,
169	but only by the most recent
170	<citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>,
171	<citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry>,
172	<citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>, and
173	<citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry> commands.
174	</para>
175	<para>
176	No commands are issued for maps that are not enabled.
177	If more than one texture evaluation is enabled for a particular dimension
178	(for example, <constant>GL_MAP2_TEXTURE_COORD_1</constant> and
179	<constant>GL_MAP2_TEXTURE_COORD_2</constant>),
180	then only the evaluation of the map that produces the larger
181	number of coordinates
182	(in this case, <constant>GL_MAP2_TEXTURE_COORD_2</constant>)
183	is carried out.
184	<constant>GL_MAP1_VERTEX_4</constant> overrides <constant>GL_MAP1_VERTEX_3</constant>,
185	and
186	<constant>GL_MAP2_VERTEX_4</constant> overrides <constant>GL_MAP2_VERTEX_3</constant>,
187	in the same manner.
188	If neither a three- nor a four-component vertex map is enabled for the
189	specified dimension,
190	the <function>glEvalCoord</function> command is ignored.
191	</para>
192	<para>
193	If you have enabled automatic normal generation,
194	by calling <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> with argument <constant>GL_AUTO_NORMAL</constant>,
195	<function>glEvalCoord2</function> generates surface normals analytically,
196	regardless of the contents or enabling of the <constant>GL_MAP2_NORMAL</constant> map.
197	Let
198	</para>
199	<para>
200	<informalequation><mml:math>
201	<!-- eqn: bold m = { {partial bold p} over {partial u} } times { {partial bold p} over {partial v} }:-->
202	<mml:mrow>
203	<mml:mi mathvariant="bold">m</mml:mi>
204	<mml:mo>=</mml:mo>
205	<mml:mrow>
206	<mml:mfenced open="" close="">
207	<mml:mfrac>
208	<mml:mfenced open="" close="">
209	<mml:mrow>
210	<mml:mo>&PartialD;</mml:mo>
211	<mml:mi mathvariant="bold">p</mml:mi>
212	</mml:mrow>
213	</mml:mfenced>
214	<mml:mfenced open="" close="">
215	<mml:mrow>
216	<mml:mo>&PartialD;</mml:mo>
217	<mml:mi mathvariant="italic">u</mml:mi>
218	</mml:mrow>
219	</mml:mfenced>
220	</mml:mfrac>
221	</mml:mfenced>
222	<mml:mo>×</mml:mo>
223	<mml:mfenced open="" close="">
224	<mml:mfrac>
225	<mml:mfenced open="" close="">
226	<mml:mrow>
227	<mml:mo>&PartialD;</mml:mo>
228	<mml:mi mathvariant="bold">p</mml:mi>
229	</mml:mrow>
230	</mml:mfenced>
231	<mml:mfenced open="" close="">
232	<mml:mrow>
233	<mml:mo>&PartialD;</mml:mo>
234	<mml:mi mathvariant="italic">v</mml:mi>
235	</mml:mrow>
236	</mml:mfenced>
237	</mml:mfrac>
238	</mml:mfenced>
239	</mml:mrow>
240	</mml:mrow>
241	</mml:math></informalequation>
242	</para>
243	<para>
244	Then the generated normal
245	<inlineequation><mml:math>
246	<!-- eqn: bold n:-->
247	<mml:mi mathvariant="bold">n</mml:mi>
248	</mml:math></inlineequation>
249	is
250	<inlineequation><mml:math>
251	<!-- eqn: bold n = bold m over { \|\| bold m \|\| }:-->
252	<mml:mrow>
253	<mml:mi mathvariant="bold">n</mml:mi>
254	<mml:mo>=</mml:mo>
255	<mml:mfrac>
256	<mml:mi mathvariant="bold">m</mml:mi>
257	<mml:mfenced open="" close="">
258	<mml:mfenced open="&DoubleVerticalBar;" close="&DoubleVerticalBar;">
259	<mml:mi mathvariant="bold">m</mml:mi>
260	</mml:mfenced>
261	</mml:mfenced>
262	</mml:mfrac>
263	</mml:mrow>
264	</mml:math></inlineequation>
265	</para>
266	<para>
267	If automatic normal generation is disabled,
268	the corresponding normal map <constant>GL_MAP2_NORMAL</constant>,
269	if enabled,
270	is used to produce a normal.
271	If neither automatic normal generation nor a normal map is enabled,
272	no normal is generated for
273	<function>glEvalCoord2</function> commands.
274	</para>
275	</refsect1>
276	<refsect1 id="associatedgets"><title>Associated Gets</title>
277	<para>
278	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_3</constant>
279	</para>
280	<para>
281	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_VERTEX_4</constant>
282	</para>
283	<para>
284	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_INDEX</constant>
285	</para>
286	<para>
287	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_COLOR_4</constant>
288	</para>
289	<para>
290	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_NORMAL</constant>
291	</para>
292	<para>
293	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_1</constant>
294	</para>
295	<para>
296	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_2</constant>
297	</para>
298	<para>
299	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_3</constant>
300	</para>
301	<para>
302	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP1_TEXTURE_COORD_4</constant>
303	</para>
304	<para>
305	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_VERTEX_3</constant>
306	</para>
307	<para>
308	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_VERTEX_4</constant>
309	</para>
310	<para>
311	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_INDEX</constant>
312	</para>
313	<para>
314	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_COLOR_4</constant>
315	</para>
316	<para>
317	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_NORMAL</constant>
318	</para>
319	<para>
320	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_1</constant>
321	</para>
322	<para>
323	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_2</constant>
324	</para>
325	<para>
326	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_3</constant>
327	</para>
328	<para>
329	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MAP2_TEXTURE_COORD_4</constant>
330	</para>
331	<para>
332	<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_AUTO_NORMAL</constant>
333	</para>
334	<para>
335	<citerefentry><refentrytitle>glGetMap</refentrytitle></citerefentry>
336	</para>
337	</refsect1>
338	<refsect1 id="seealso"><title>See Also</title>
339	<para>
340	<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>,
341	<citerefentry><refentrytitle>glColor</refentrytitle></citerefentry>,
342	<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
343	<citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>,
344	<citerefentry><refentrytitle>glEvalPoint</refentrytitle></citerefentry>,
345	<citerefentry><refentrytitle>glIndex</refentrytitle></citerefentry>,
346	<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>,
347	<citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>,
348	<citerefentry><refentrytitle>glMapGrid</refentrytitle></citerefentry>,
349	<citerefentry><refentrytitle>glNormal</refentrytitle></citerefentry>,
350	<citerefentry><refentrytitle>glTexCoord</refentrytitle></citerefentry>,
351	<citerefentry><refentrytitle>glVertex</refentrytitle></citerefentry>
352	</para>
353	</refsect1>
354	<refsect1 id="Copyright"><title>Copyright</title>
355	<para>
356	Copyright <trademark class="copyright"></trademark> 1991-2006
357	Silicon Graphics, Inc. This document is licensed under the SGI
358	Free Software B License. For details, see
359	<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
360	</para>
361	</refsect1>
362	</refentry>