--- /dev/null
+<?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="glPolygonOffset">
+ <refmeta>
+ <refmetainfo>
+ <copyright>
+ <year>1991-2006</year>
+ <holder>Silicon Graphics, Inc.</holder>
+ </copyright>
+ </refmetainfo>
+ <refentrytitle>glPolygonOffset</refentrytitle>
+ <manvolnum>3G</manvolnum>
+ </refmeta>
+ <refnamediv>
+ <refname>glPolygonOffset</refname>
+ <refpurpose>set the scale and units used to calculate depth values</refpurpose>
+ </refnamediv>
+ <refsynopsisdiv><title>C Specification</title>
+ <funcsynopsis>
+ <funcprototype>
+ <funcdef>void <function>glPolygonOffset</function></funcdef>
+ <paramdef>GLfloat <parameter>factor</parameter></paramdef>
+ <paramdef>GLfloat <parameter>units</parameter></paramdef>
+ </funcprototype>
+ </funcsynopsis>
+ </refsynopsisdiv>
+ <!-- eqn: ignoring delim $$ -->
+ <refsect1 id="parameters"><title>Parameters</title>
+ <variablelist>
+ <varlistentry>
+ <term><parameter>factor</parameter></term>
+ <listitem>
+ <para>
+ Specifies a scale factor that is used to create a variable
+ depth offset for each polygon. The initial value is 0.
+ </para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term><parameter>units</parameter></term>
+ <listitem>
+ <para>
+ Is multiplied by an implementation-specific value to
+ create a constant depth offset. The initial value is 0.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </refsect1>
+ <refsect1 id="description"><title>Description</title>
+ <para>
+ When <constant>GL_POLYGON_OFFSET_FILL</constant>, <constant>GL_POLYGON_OFFSET_LINE</constant>, or
+ <constant>GL_POLYGON_OFFSET_POINT</constant> is enabled, each
+ fragment's <emphasis>depth</emphasis> value will be offset after it is interpolated
+ from the <emphasis>depth</emphasis> values of the appropriate vertices.
+ The value of the offset is
+ <inlineequation><mml:math>
+ <!-- eqn: factor * DZ + r * units:-->
+ <mml:mrow>
+ <mml:mrow>
+ <mml:mi mathvariant="italic">factor</mml:mi>
+ <mml:mo>×</mml:mo>
+ <mml:mi mathvariant="italic">DZ</mml:mi>
+ </mml:mrow>
+ <mml:mo>+</mml:mo>
+ <mml:mrow>
+ <mml:mi mathvariant="italic">r</mml:mi>
+ <mml:mo>×</mml:mo>
+ <mml:mi mathvariant="italic">units</mml:mi>
+ </mml:mrow>
+ </mml:mrow>
+ </mml:math></inlineequation>,
+ where
+ <inlineequation><mml:math>
+ <!-- eqn: DZ:-->
+ <mml:mi mathvariant="italic">DZ</mml:mi>
+ </mml:math></inlineequation>
+ is a measurement of the change in depth relative to the screen
+ area of the polygon, and
+ <inlineequation><mml:math><mml:mi mathvariant="italic">r</mml:mi></mml:math></inlineequation>
+ is the smallest value that is guaranteed to
+ produce a resolvable offset for a given implementation.
+ The offset is added before the depth test is performed and before
+ the value is written into the depth buffer.
+ </para>
+ <para>
+ <function>glPolygonOffset</function> is useful for rendering hidden-line images, for applying decals
+ to surfaces, and for rendering solids with highlighted edges.
+ </para>
+ </refsect1>
+ <refsect1 id="notes"><title>Notes</title>
+ <para>
+ <function>glPolygonOffset</function> is available only if the GL version is 1.1 or greater.
+ </para>
+ <para>
+ <function>glPolygonOffset</function> has no effect on depth coordinates placed in the
+ feedback buffer.
+ </para>
+ <para>
+ <function>glPolygonOffset</function> has no effect on selection.
+ </para>
+ </refsect1>
+ <refsect1 id="errors"><title>Errors</title>
+ <para>
+ <constant>GL_INVALID_OPERATION</constant> is generated if <function>glPolygonOffset</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>glIsEnabled</refentrytitle></citerefentry> with argument
+ <constant>GL_POLYGON_OFFSET_FILL</constant>,
+ <constant>GL_POLYGON_OFFSET_LINE</constant>,
+ or <constant>GL_POLYGON_OFFSET_POINT</constant>.
+ </para>
+ <para>
+ <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_POLYGON_OFFSET_FACTOR</constant> or
+ <constant>GL_POLYGON_OFFSET_UNITS</constant>.
+ </para>
+ </refsect1>
+ <refsect1 id="seealso"><title>See Also</title>
+ <para>
+ <citerefentry><refentrytitle>glDepthFunc</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry>,
+ <citerefentry><refentrytitle>glIsEnabled</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>
HCoop / clinton / guile-figl.git / blobdiff