165 lines
7.8 KiB
XML
165 lines
7.8 KiB
XML
<?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="glLineStipple">
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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>glLineStipple</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glLineStipple</refname>
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<refpurpose>specify the line stipple pattern</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>glLineStipple</function></funcdef>
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<paramdef>GLint <parameter>factor</parameter></paramdef>
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<paramdef>GLushort <parameter>pattern</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>factor</parameter></term>
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<listitem>
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<para>
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Specifies a multiplier for each bit in the line stipple pattern.
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If <parameter>factor</parameter> is 3,
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for example,
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each bit in the pattern is used three times
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before the next bit in the pattern is used.
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<parameter>factor</parameter> is clamped to the range [1, 256] and defaults to 1.
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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>pattern</parameter></term>
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<listitem>
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<para>
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Specifies a 16-bit integer whose bit pattern determines
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which fragments of a line will be drawn when the line is rasterized.
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Bit zero is used first; the default pattern is all 1's.
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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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Line stippling masks out certain fragments produced by rasterization;
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those fragments will not be drawn.
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The masking is achieved by using three parameters:
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the 16-bit line stipple pattern <parameter>pattern</parameter>,
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the repeat count <parameter>factor</parameter>,
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and an integer stipple counter
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<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>.
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</para>
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<para>
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Counter
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<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
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is reset to 0 whenever <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> is called
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and before each line segment of a <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>(<constant>GL_LINES</constant>)/<citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>
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sequence is generated.
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It is incremented after each fragment of a unit width aliased line segment
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is generated
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or after each
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<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
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fragments of an
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<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
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width line segment are generated.
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The
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<inlineequation><mml:math><mml:mi mathvariant="italic">i</mml:mi></mml:math></inlineequation>
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fragments associated with count
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<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
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are masked out if
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</para>
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<para>
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<parameter>pattern</parameter> bit
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<inlineequation><mml:math>
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<!-- eqn: (s / factor) mod 16:-->
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<mml:mrow>
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<mml:mfenced open="(" close=")">
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<mml:mfrac>
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<mml:mi mathvariant="italic">s</mml:mi>
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<mml:mi mathvariant="italic">factor</mml:mi>
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</mml:mfrac>
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</mml:mfenced>
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<mml:mo>%</mml:mo>
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<mml:mn>16</mml:mn>
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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 0, otherwise these fragments are sent to the frame buffer.
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Bit zero of <parameter>pattern</parameter> is the least significant bit.
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</para>
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<para>
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Antialiased lines are treated as a sequence of
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<inlineequation><mml:math>
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<!-- eqn: 1 times width:-->
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<mml:mrow>
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<mml:mn>1</mml:mn>
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<mml:mo>×</mml:mo>
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<mml:mi mathvariant="italic">width</mml:mi>
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</mml:mrow>
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</mml:math></inlineequation>
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rectangles
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for purposes of stippling.
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Whether rectangle
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<inlineequation><mml:math><mml:mi mathvariant="italic">s</mml:mi></mml:math></inlineequation>
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is rasterized or not depends on the fragment rule
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described for aliased lines,
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counting rectangles rather than groups of fragments.
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</para>
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<para>
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To enable and disable line stippling, call <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry> and <citerefentry><refentrytitle>glDisable</refentrytitle></citerefentry>
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with argument <constant>GL_LINE_STIPPLE</constant>.
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When enabled,
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the line stipple pattern is applied as described above.
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When disabled,
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it is as if the pattern were all 1's.
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Initially, line stippling is disabled.
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</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para>
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<constant>GL_INVALID_OPERATION</constant> is generated if <function>glLineStipple</function>
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is executed between the execution of <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
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and the corresponding execution of <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.
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</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LINE_STIPPLE_PATTERN</constant>
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</para>
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<para>
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<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_LINE_STIPPLE_REPEAT</constant>
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</para>
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<para>
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<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_LINE_STIPPLE</constant>
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</para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para>
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<citerefentry><refentrytitle>glLineWidth</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glPolygonStipple</refentrytitle></citerefentry>
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</para>
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</refsect1>
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<refsect1 id="Copyright"><title>Copyright</title>
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<para>
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Copyright <trademark class="copyright"></trademark> 1991-2006
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Silicon Graphics, Inc. This document is licensed under the SGI
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Free Software B License. For details, see
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<ulink url="http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/</ulink>.
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</para>
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</refsect1>
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</refentry>
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