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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"> | |
5 | <refmeta> | |
6 | <refmetainfo> | |
7 | <copyright> | |
8 | <year>1991-2006</year> | |
9 | <holder>Silicon Graphics, Inc.</holder> | |
10 | </copyright> | |
11 | </refmetainfo> | |
12 | <refentrytitle>glSampleCoverage</refentrytitle> | |
13 | <manvolnum>3G</manvolnum> | |
14 | </refmeta> | |
15 | <refnamediv> | |
16 | <refname>glSampleCoverage</refname> | |
17 | <refpurpose>specify multisample coverage parameters</refpurpose> | |
18 | </refnamediv> | |
19 | <refsynopsisdiv><title>C Specification</title> | |
20 | <funcsynopsis> | |
21 | <funcprototype> | |
22 | <funcdef>void <function>glSampleCoverage</function></funcdef> | |
23 | <paramdef>GLfloat <parameter>value</parameter></paramdef> | |
24 | <paramdef>GLboolean <parameter>invert</parameter></paramdef> | |
25 | </funcprototype> | |
26 | </funcsynopsis> | |
27 | </refsynopsisdiv> | |
28 | <!-- eqn: ignoring delim $$ --> | |
29 | <refsect1 id="parameters"><title>Parameters</title> | |
30 | <variablelist> | |
31 | <varlistentry> | |
32 | <term><parameter>value</parameter></term> | |
33 | <listitem> | |
34 | <para> | |
35 | Specify a single floating-point sample coverage value. The value is | |
36 | clamped to the range | |
37 | <inlineequation><mml:math> | |
38 | <!-- eqn: [0 ,1]: --> | |
39 | <mml:mfenced open="[" close="]"> | |
40 | <mml:mn>0</mml:mn> | |
41 | <mml:mn>1</mml:mn> | |
42 | </mml:mfenced> | |
43 | </mml:math></inlineequation>. | |
44 | The initial value is 1.0. | |
45 | </para> | |
46 | </listitem> | |
47 | </varlistentry> | |
48 | <varlistentry> | |
49 | <term><parameter>invert</parameter></term> | |
50 | <listitem> | |
51 | <para> | |
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>. | |
55 | </para> | |
56 | </listitem> | |
57 | </varlistentry> | |
58 | </variablelist> | |
59 | </refsect1> | |
60 | <refsect1 id="description"><title>Description</title> | |
61 | <para> | |
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. | |
66 | </para> | |
67 | <para> | |
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. | |
73 | </para> | |
74 | <para> | |
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. | |
78 | </para> | |
79 | <para> | |
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. | |
84 | </para> | |
85 | </refsect1> | |
86 | <refsect1 id="notes"><title>Notes</title> | |
87 | <para> | |
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> | |
92 | page. | |
93 | </para> | |
94 | </refsect1> | |
95 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
96 | <para> | |
97 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_VALUE</constant> | |
98 | </para> | |
99 | <para> | |
100 | <citerefentry><refentrytitle>glGet</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE_INVERT</constant> | |
101 | </para> | |
102 | <para> | |
103 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_MULTISAMPLE</constant> | |
104 | </para> | |
105 | <para> | |
106 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_COVERAGE</constant> | |
107 | </para> | |
108 | <para> | |
109 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_ALPHA_TO_ONE</constant> | |
110 | </para> | |
111 | <para> | |
112 | <citerefentry><refentrytitle>glIsEnabled</refentrytitle></citerefentry> with argument <constant>GL_SAMPLE_COVERAGE</constant> | |
113 | </para> | |
114 | </refsect1> | |
115 | <refsect1 id="seealso"><title>See Also</title> | |
116 | <para> | |
117 | <citerefentry><refentrytitle>glEnable</refentrytitle></citerefentry>, | |
118 | <citerefentry><refentrytitle>removedTypes</refentrytitle></citerefentry> | |
119 | </para> | |
120 | </refsect1> | |
121 | <refsect1 id="Copyright"><title>Copyright</title> | |
122 | <para> | |
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>. | |
127 | </para> | |
128 | </refsect1> | |
129 | </refentry> |