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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook MathML Module V1.1b1//EN"
"http://www.oasis-open.org/docbook/xml/mathml/1.1CR1/dbmathml.dtd">
<refentry id="glMapGrid">
<refmeta>
<refmetainfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
</refmetainfo>
<refentrytitle>glMapGrid</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glMapGrid</refname>
<refpurpose>define a one- or two-dimensional mesh</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glMapGrid1d</function></funcdef>
<paramdef>GLint <parameter>un</parameter></paramdef>
<paramdef>GLdouble <parameter>u1</parameter></paramdef>
<paramdef>GLdouble <parameter>u2</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glMapGrid1f</function></funcdef>
<paramdef>GLint <parameter>un</parameter></paramdef>
<paramdef>GLfloat <parameter>u1</parameter></paramdef>
<paramdef>GLfloat <parameter>u2</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glMapGrid2d</function></funcdef>
<paramdef>GLint <parameter>un</parameter></paramdef>
<paramdef>GLdouble <parameter>u1</parameter></paramdef>
<paramdef>GLdouble <parameter>u2</parameter></paramdef>
<paramdef>GLint <parameter>vn</parameter></paramdef>
<paramdef>GLdouble <parameter>v1</parameter></paramdef>
<paramdef>GLdouble <parameter>v2</parameter></paramdef>
</funcprototype>
</funcsynopsis>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glMapGrid2f</function></funcdef>
<paramdef>GLint <parameter>un</parameter></paramdef>
<paramdef>GLfloat <parameter>u1</parameter></paramdef>
<paramdef>GLfloat <parameter>u2</parameter></paramdef>
<paramdef>GLint <parameter>vn</parameter></paramdef>
<paramdef>GLfloat <parameter>v1</parameter></paramdef>
<paramdef>GLfloat <parameter>v2</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<!-- eqn: ignoring delim $$ -->
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>un</parameter></term>
<listitem>
<para>
Specifies the number of partitions in the grid range interval
[<parameter>u1</parameter>, <parameter>u2</parameter>].
Must be positive.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>u1</parameter></term>
<term><parameter>u2</parameter></term>
<listitem>
<para>
Specify the mappings for integer grid domain values
<inlineequation><mml:math>
<!-- eqn: i = 0:-->
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>=</mml:mo>
<mml:mn>0</mml:mn>
</mml:mrow>
</mml:math></inlineequation>
and
<inlineequation><mml:math>
<!-- eqn: i = un:-->
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi mathvariant="italic">un</mml:mi>
</mml:mrow>
</mml:math></inlineequation>.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>vn</parameter></term>
<listitem>
<para>
Specifies the number of partitions in the grid range interval
[<parameter>v1</parameter>, <parameter>v2</parameter>]
(<function>glMapGrid2</function> only).
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>v1</parameter></term>
<term><parameter>v2</parameter></term>
<listitem>
<para>
Specify the mappings for integer grid domain values
<inlineequation><mml:math>
<!-- eqn: j = 0:-->
<mml:mrow>
<mml:mi mathvariant="italic">j</mml:mi>
<mml:mo>=</mml:mo>
<mml:mn>0</mml:mn>
</mml:mrow>
</mml:math></inlineequation>
and
<inlineequation><mml:math>
<!-- eqn: j = vn:-->
<mml:mrow>
<mml:mi mathvariant="italic">j</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi mathvariant="italic">vn</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
(<function>glMapGrid2</function> only).
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
<function>glMapGrid</function> and <citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry> are used together to efficiently
generate and evaluate a series of evenly-spaced map domain values.
<citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry> steps through the integer domain
of a one- or two-dimensional grid,
whose range is the domain of the evaluation maps specified by
<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry>.
</para>
<para>
<function>glMapGrid1</function> and <function>glMapGrid2</function> specify the linear grid mappings
between the
<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
(or
<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">j</mml:mi></mml:math></inlineequation>)
integer grid coordinates,
to the
<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
(or
<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>)
floating-point evaluation map coordinates.
See <citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glMap2</refentrytitle></citerefentry> for details of how
<inlineequation><mml:math><mml:mi mathvariant="italic">u</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">v</mml:mi></mml:math></inlineequation>
coordinates
are evaluated.
</para>
<para>
<function>glMapGrid1</function> specifies a single linear mapping
such that integer grid coordinate 0 maps exactly to <parameter>u1</parameter>,
and integer grid coordinate <parameter>un</parameter> maps exactly to <parameter>u2</parameter>.
All other integer grid coordinates
<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
are mapped so that
</para>
<para>
<informalequation><mml:math>
<!-- eqn: u = i (u2 - u1) / un + u1:-->
<mml:mrow>
<mml:mi mathvariant="italic">u</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:mi mathvariant="italic">u2</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">u1</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mi mathvariant="italic">un</mml:mi>
</mml:mfrac>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">u1</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</para>
<para>
<function>glMapGrid2</function> specifies two such linear mappings.
One maps integer grid coordinate
<inlineequation><mml:math>
<!-- eqn: i = 0:-->
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>=</mml:mo>
<mml:mn>0</mml:mn>
</mml:mrow>
</mml:math></inlineequation>
exactly to <parameter>u1</parameter>,
and integer grid coordinate
<inlineequation><mml:math>
<!-- eqn: i = un:-->
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi mathvariant="italic">un</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
exactly to <parameter>u2</parameter>.
The other maps integer grid coordinate
<inlineequation><mml:math>
<!-- eqn: j = 0:-->
<mml:mrow>
<mml:mi mathvariant="italic">j</mml:mi>
<mml:mo>=</mml:mo>
<mml:mn>0</mml:mn>
</mml:mrow>
</mml:math></inlineequation>
exactly to <parameter>v1</parameter>,
and integer grid coordinate
<inlineequation><mml:math>
<!-- eqn: j = vn:-->
<mml:mrow>
<mml:mi mathvariant="italic">j</mml:mi>
<mml:mo>=</mml:mo>
<mml:mi mathvariant="italic">vn</mml:mi>
</mml:mrow>
</mml:math></inlineequation>
exactly to <parameter>v2</parameter>.
Other integer grid coordinates
<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
and
<inlineequation><mml:math><mml:mi mathvariant="italic">j</mml:mi></mml:math></inlineequation>
are mapped such that
</para>
<para>
<informalequation><mml:math>
<!-- eqn: u = i (u2 - u1) / un + u1:-->
<mml:mrow>
<mml:mi mathvariant="italic">u</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi mathvariant="italic">i</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:mi mathvariant="italic">u2</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">u1</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mi mathvariant="italic">un</mml:mi>
</mml:mfrac>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">u1</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</para>
<para>
<informalequation><mml:math>
<!-- eqn: v = j (v2 - v1) / vn + v1:-->
<mml:mrow>
<mml:mi mathvariant="italic">v</mml:mi>
<mml:mo>=</mml:mo>
<mml:mrow>
<mml:mfrac>
<mml:mrow>
<mml:mi mathvariant="italic">j</mml:mi>
<mml:mo>⁡</mml:mo>
<mml:mfenced open="(" close=")">
<mml:mrow>
<mml:mi mathvariant="italic">v2</mml:mi>
<mml:mo>-</mml:mo>
<mml:mi mathvariant="italic">v1</mml:mi>
</mml:mrow>
</mml:mfenced>
</mml:mrow>
<mml:mi mathvariant="italic">vn</mml:mi>
</mml:mfrac>
<mml:mo>+</mml:mo>
<mml:mi mathvariant="italic">v1</mml:mi>
</mml:mrow>
</mml:mrow>
</mml:math></informalequation>
</para>
<para>
The mappings specified by <function>glMapGrid</function> are used identically by
<citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glEvalPoint</refentrytitle></citerefentry>.
</para>
</refsect1>
<refsect1 id="errors"><title>Errors</title>
<para>
<constant>GL_INVALID_VALUE</constant> is generated if either <parameter>un</parameter> or <parameter>vn</parameter> is not
positive.
</para>
<para>
<constant>GL_INVALID_OPERATION</constant> is generated if <function>glMapGrid</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>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP1_GRID_DOMAIN</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP2_GRID_DOMAIN</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP1_GRID_SEGMENTS</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_MAP2_GRID_SEGMENTS</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glEvalCoord</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalMesh</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glEvalPoint</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMap1</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>glMap2</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>