1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
|
<?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="glSampleCoverage">
<refentryinfo>
<copyright>
<year>1991-2006</year>
<holder>Silicon Graphics, Inc.</holder>
</copyright>
<copyright>
<year>2010-2013</year>
<holder>Khronos Group</holder>
</copyright>
</refentryinfo>
<refmeta>
<refentrytitle>glSampleCoverage</refentrytitle>
<manvolnum>3G</manvolnum>
</refmeta>
<refnamediv>
<refname>glSampleCoverage</refname>
<refpurpose>specify multisample coverage parameters</refpurpose>
</refnamediv>
<refsynopsisdiv><title>C Specification</title>
<funcsynopsis>
<funcprototype>
<funcdef>void <function>glSampleCoverage</function></funcdef>
<paramdef>GLfloat <parameter>value</parameter></paramdef>
<paramdef>GLboolean <parameter>invert</parameter></paramdef>
</funcprototype>
</funcsynopsis>
</refsynopsisdiv>
<refsect1 id="parameters"><title>Parameters</title>
<variablelist>
<varlistentry>
<term><parameter>value</parameter></term>
<listitem>
<para>
Specify a single floating-point sample coverage value. The value is
clamped to the range
<inlineequation><mml:math>
<!-- eqn: [0 ,1]: -->
<mml:mfenced open="[" close="]">
<mml:mn>0</mml:mn>
<mml:mn>1</mml:mn>
</mml:mfenced>
</mml:math></inlineequation>.
The initial value is 1.0.
</para>
</listitem>
</varlistentry>
<varlistentry>
<term><parameter>invert</parameter></term>
<listitem>
<para>
Specify a single boolean value representing if the coverage masks should be
inverted. <constant>GL_TRUE</constant> and <constant>GL_FALSE</constant> are accepted. The initial value
is <constant>GL_FALSE</constant>.
</para>
</listitem>
</varlistentry>
</variablelist>
</refsect1>
<refsect1 id="description"><title>Description</title>
<para>
Multisampling samples a pixel multiple times at various
implementation-dependent subpixel locations to generate antialiasing
effects. Multisampling transparently antialiases points, lines, polygons,
and images if it is enabled.
</para>
<para>
<parameter>value</parameter> is used in constructing a temporary mask used in determining which
samples will be used in resolving the final fragment color. This mask is
bitwise-anded with the coverage mask generated from the multisampling
computation. If the <parameter>invert</parameter> flag is set, the temporary mask is inverted
(all bits flipped) and then the bitwise-and is computed.
</para>
<para>
If an implementation does not have any multisample buffers available, or
multisampling is disabled, rasterization occurs with only a single sample
computing a pixel's final RGB color.
</para>
<para>
Provided an implementation supports multisample buffers, and multisampling
is enabled, then a pixel's final color is generated by combining several
samples per pixel. Each sample contains color, depth, and stencil
information, allowing those operations to be performed on each sample.
</para>
</refsect1>
<refsect1 id="notes"><title>Notes</title>
<para>
The type of the <parameter>value</parameter> parameter was
changed from GLclampf to GLfloat. This change is transparent
to user code and is described in detail on the
<citerefentry><refentrytitle>removedTypes</refentrytitle></citerefentry>
page.
</para>
</refsect1>
<refsect1 id="associatedgets"><title>Associated Gets</title>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_VALUE</constant>
</para>
<para>
<citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_INVERT</constant>
</para>
<para>
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MULTISAMPLE</constant>
</para>
<para>
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant>
</para>
<para>
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_ONE</constant>
</para>
<para>
<citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE</constant>
</para>
</refsect1>
<refsect1 id="seealso"><title>See Also</title>
<para>
<citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>,
<citerefentry><refentrytitle>removedTypes</refentrytitle></citerefentry>
</para>
</refsect1>
<refsect1 id="Copyright"><title>Copyright</title>
<para>
Copyright <trademark class="copyright"></trademark> 1991-2006 Silicon Graphics, Inc.
Copyright <trademark class="copyright"></trademark> 2010-2013 Khronos Group.
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>
|
