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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="glGetUniform"> | |
5 | <refmeta> | |
6 | <refentrytitle>glGetUniform</refentrytitle> | |
7 | <manvolnum>3G</manvolnum> | |
8 | </refmeta> | |
9 | <refnamediv> | |
10 | <refdescriptor>glGetUniform</refdescriptor> | |
11 | <refname>glGetUniformfv</refname> | |
12 | <refname>glGetUniformiv</refname> | |
13 | <refpurpose>Returns the value of a uniform variable</refpurpose> | |
14 | </refnamediv> | |
15 | <refsynopsisdiv><title>C Specification</title> | |
16 | <funcsynopsis> | |
17 | <funcprototype> | |
18 | <funcdef>void <function>glGetUniformfv</function></funcdef> | |
19 | <paramdef>GLuint <parameter>program</parameter></paramdef> | |
20 | <paramdef>GLint <parameter>location</parameter></paramdef> | |
21 | <paramdef>GLfloat *<parameter>params</parameter></paramdef> | |
22 | </funcprototype> | |
23 | <funcprototype> | |
24 | <funcdef>void <function>glGetUniformiv</function></funcdef> | |
25 | <paramdef>GLuint <parameter>program</parameter></paramdef> | |
26 | <paramdef>GLint <parameter>location</parameter></paramdef> | |
27 | <paramdef>GLint *<parameter>params</parameter></paramdef> | |
28 | </funcprototype> | |
29 | </funcsynopsis> | |
30 | </refsynopsisdiv> | |
31 | <refsect1 id="parameters"><title>Parameters</title> | |
32 | <variablelist> | |
33 | <varlistentry> | |
34 | <term><parameter>program</parameter></term> | |
35 | <listitem> | |
36 | <para>Specifies the program object to be | |
37 | queried.</para> | |
38 | </listitem> | |
39 | </varlistentry> | |
40 | <varlistentry> | |
41 | <term><parameter>location</parameter></term> | |
42 | <listitem> | |
43 | <para>Specifies the location of the uniform variable | |
44 | to be queried.</para> | |
45 | </listitem> | |
46 | </varlistentry> | |
47 | <varlistentry> | |
48 | <term><parameter>params</parameter></term> | |
49 | <listitem> | |
50 | <para>Returns the value of the specified uniform | |
51 | variable.</para> | |
52 | </listitem> | |
53 | </varlistentry> | |
54 | </variablelist> | |
55 | </refsect1> | |
56 | <refsect1 id="description"><title>Description</title> | |
57 | <para><function>glGetUniform</function> returns in | |
58 | <parameter>params</parameter> the value(s) of the specified | |
59 | uniform variable. The type of the uniform variable specified by | |
60 | <parameter>location</parameter> determines the number of values | |
61 | returned. If the uniform variable is defined in the shader as a | |
62 | boolean, int, or float, a single value will be returned. If it | |
63 | is defined as a vec2, ivec2, or bvec2, two values will be | |
64 | returned. If it is defined as a vec3, ivec3, or bvec3, three | |
65 | values will be returned, and so on. To query values stored in | |
66 | uniform variables declared as arrays, call | |
67 | <function>glGetUniform</function> for each element of the array. | |
68 | To query values stored in uniform variables declared as | |
69 | structures, call <function>glGetUniform</function> for each | |
70 | field in the structure. The values for uniform variables | |
71 | declared as a matrix will be returned in column major | |
72 | order.</para> | |
73 | ||
74 | <para>The locations assigned to uniform variables are not known | |
75 | until the program object is linked. After linking has occurred, | |
76 | the command | |
77 | <citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry> | |
78 | can be used to obtain the location of a uniform variable. This | |
79 | location value can then be passed to | |
80 | <function>glGetUniform</function> in order to query the current | |
81 | value of the uniform variable. After a program object has been | |
82 | linked successfully, the index values for uniform variables | |
83 | remain fixed until the next link command occurs. The uniform | |
84 | variable values can only be queried after a link if the link was | |
85 | successful.</para> | |
86 | </refsect1> | |
87 | <refsect1 id="notes"><title>Notes</title> | |
88 | <para><function>glGetUniform</function> is available only if the | |
89 | GL version is 2.0 or greater.</para> | |
90 | ||
91 | <para>If an error is generated, no change is made to the | |
92 | contents of <parameter>params</parameter>.</para> | |
93 | </refsect1> | |
94 | <refsect1 id="errors"><title>Errors</title> | |
95 | <para><constant>GL_INVALID_VALUE</constant> is generated if | |
96 | <parameter>program</parameter> is not a value generated by | |
97 | OpenGL.</para> | |
98 | ||
99 | <para><constant>GL_INVALID_OPERATION</constant> is generated if | |
100 | <parameter>program</parameter> is not a program object.</para> | |
101 | ||
102 | <para><constant>GL_INVALID_OPERATION</constant> is generated if | |
103 | <parameter>program</parameter> has not been successfully | |
104 | linked.</para> | |
105 | ||
106 | <para><constant>GL_INVALID_OPERATION</constant> is generated if | |
107 | <parameter>location</parameter> does not correspond to a valid | |
108 | uniform variable location for the specified program object.</para> | |
109 | ||
110 | <para><constant>GL_INVALID_OPERATION</constant> is generated if | |
111 | <function>glGetUniform</function> is executed between the | |
112 | execution of | |
113 | <citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry> | |
114 | and the corresponding execution of | |
115 | <citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.</para> | |
116 | </refsect1> | |
117 | <refsect1 id="associatedgets"><title>Associated Gets</title> | |
118 | <para><citerefentry><refentrytitle>glGetActiveUniform</refentrytitle></citerefentry> | |
119 | with arguments <parameter>program</parameter> and the index of an active | |
120 | uniform variable</para> | |
121 | ||
122 | <para><citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry> | |
123 | with arguments <parameter>program</parameter> and | |
124 | <constant>GL_ACTIVE_UNIFORMS</constant> or | |
125 | <constant>GL_ACTIVE_UNIFORM_MAX_LENGTH</constant></para> | |
126 | ||
127 | <para><citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry> | |
128 | with arguments <parameter>program</parameter> and the name of a | |
129 | uniform variable</para> | |
130 | <para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para> | |
131 | </refsect1> | |
132 | <refsect1 id="seealso"><title>See Also</title> | |
133 | <para><citerefentry><refentrytitle>glCreateProgram</refentrytitle></citerefentry>, | |
134 | <citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>, | |
135 | <citerefentry><refentrytitle>glUniform</refentrytitle></citerefentry></para> | |
136 | </refsect1> | |
137 | <refsect1 id="Copyright"><title>Copyright</title> | |
138 | <para> | |
139 | Copyright <trademark class="copyright"></trademark> 2003-2005 3Dlabs Inc. Ltd. | |
140 | This material may be distributed subject to the terms and conditions set forth in | |
141 | the Open Publication License, v 1.0, 8 June 1999. | |
142 | <ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>. | |
143 | </para> | |
144 | </refsect1> | |
145 | </refentry> |