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=
"glSampleCoverage">
9 <holder>Silicon Graphics, Inc.
</holder>
12 <refentrytitle>glSampleCoverage
</refentrytitle>
13 <manvolnum>3G
</manvolnum>
16 <refname>glSampleCoverage
</refname>
17 <refpurpose>specify multisample coverage parameters
</refpurpose>
19 <refsynopsisdiv><title>C Specification
</title>
22 <funcdef>void
<function>glSampleCoverage
</function></funcdef>
23 <paramdef>GLfloat
<parameter>value
</parameter></paramdef>
24 <paramdef>GLboolean
<parameter>invert
</parameter></paramdef>
28 <!-- eqn: ignoring delim $$ -->
29 <refsect1 id=
"parameters"><title>Parameters
</title>
32 <term><parameter>value
</parameter></term>
35 Specify a single floating-point sample coverage value. The value is
37 <inlineequation><mml:math>
39 <mml:mfenced open=
"[" close=
"]">
43 </mml:math></inlineequation>.
44 The initial value is
1.0.
49 <term><parameter>invert
</parameter></term>
52 Specify a single boolean value representing if the coverage masks should be
53 inverted.
<constant>GL_TRUE
</constant> and
<constant>GL_FALSE
</constant> are accepted. The initial value
54 is
<constant>GL_FALSE
</constant>.
60 <refsect1 id=
"description"><title>Description
</title>
62 Multisampling samples a pixel multiple times at various
63 implementation-dependent subpixel locations to generate antialiasing
64 effects. Multisampling transparently antialiases points, lines, polygons,
65 and images if it is enabled.
68 <parameter>value
</parameter> is used in constructing a temporary mask used in determining which
69 samples will be used in resolving the final fragment color. This mask is
70 bitwise-anded with the coverage mask generated from the multisampling
71 computation. If the
<parameter>invert
</parameter> flag is set, the temporary mask is inverted
72 (all bits flipped) and then the bitwise-and is computed.
75 If an implementation does not have any multisample buffers available, or
76 multisampling is disabled, rasterization occurs with only a single sample
77 computing a pixel's final RGB color.
80 Provided an implementation supports multisample buffers, and multisampling
81 is enabled, then a pixel's final color is generated by combining several
82 samples per pixel. Each sample contains color, depth, and stencil
83 information, allowing those operations to be performed on each sample.
86 <refsect1 id=
"notes"><title>Notes
</title>
88 The type of the
<parameter>value
</parameter> parameter was
89 changed from GLclampf to GLfloat. This change is transparent
90 to user code and is described in detail on the
91 <citerefentry><refentrytitle>removedTypes
</refentrytitle></citerefentry>
95 <refsect1 id=
"associatedgets"><title>Associated Gets
</title>
97 <citerefentry><refentrytitle>glGet
</refentrytitle></citerefentry> with argument
<constant>GL_SAMPLE_COVERAGE_VALUE
</constant>
100 <citerefentry><refentrytitle>glGet
</refentrytitle></citerefentry> with argument
<constant>GL_SAMPLE_COVERAGE_INVERT
</constant>
103 <citerefentry><refentrytitle>glIsEnabled
</refentrytitle></citerefentry> with argument
<constant>GL_MULTISAMPLE
</constant>
106 <citerefentry><refentrytitle>glIsEnabled
</refentrytitle></citerefentry> with argument
<constant>GL_SAMPLE_ALPHA_TO_COVERAGE
</constant>
109 <citerefentry><refentrytitle>glIsEnabled
</refentrytitle></citerefentry> with argument
<constant>GL_SAMPLE_ALPHA_TO_ONE
</constant>
112 <citerefentry><refentrytitle>glIsEnabled
</refentrytitle></citerefentry> with argument
<constant>GL_SAMPLE_COVERAGE
</constant>
115 <refsect1 id=
"seealso"><title>See Also
</title>
117 <citerefentry><refentrytitle>glEnable
</refentrytitle></citerefentry>,
118 <citerefentry><refentrytitle>removedTypes
</refentrytitle></citerefentry>
121 <refsect1 id=
"Copyright"><title>Copyright
</title>
123 Copyright
<trademark class=
"copyright"></trademark> 1991-
2006
124 Silicon Graphics, Inc. This document is licensed under the SGI
125 Free Software B License. For details, see
126 <ulink url=
"http://oss.sgi.com/projects/FreeB/">http://oss.sgi.com/projects/FreeB/
</ulink>.