123 lines
5.8 KiB
XML
123 lines
5.8 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="glGetUniformLocation">
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<refmeta>
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<refentrytitle>glGetUniformLocation</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refname>glGetUniformLocation</refname>
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<refpurpose>Returns the location of a uniform variable</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>GLint <function>glGetUniformLocation</function></funcdef>
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<paramdef>GLuint <parameter>program</parameter></paramdef>
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<paramdef>const GLchar *<parameter>name</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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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>program</parameter></term>
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<listitem>
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<para>Specifies the program object to be
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queried.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>name</parameter></term>
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<listitem>
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<para>Points to a null terminated string containing
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the name of the uniform variable whose location is
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to be queried.</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><function>glGetUniformLocation </function> returns an
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integer that represents the location of a specific uniform
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variable within a program object. <parameter>name</parameter>
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must be a null terminated string that contains no white space.
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<parameter>name</parameter> must be an active uniform variable
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name in <parameter>program</parameter> that is not a structure,
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an array of structures, or a subcomponent of a vector or a
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matrix. This function returns -1 if <parameter>name</parameter>
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does not correspond to an active uniform variable in
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<parameter>program</parameter> or if <parameter>name</parameter>
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starts with the reserved prefix "gl_".</para>
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<para>Uniform variables that are structures or arrays of
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structures may be queried by calling
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<function>glGetUniformLocation</function> for each field within
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the structure. The array element operator "[]" and the
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structure field operator "." may be used in
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<parameter>name</parameter> in order to select elements within
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an array or fields within a structure. The result of using these
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operators is not allowed to be another structure, an array of
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structures, or a subcomponent of a vector or a matrix. Except if
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the last part of <parameter>name</parameter> indicates a uniform
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variable array, the location of the first element of an array
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can be retrieved by using the name of the array, or by using the
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name appended by "[0]".</para>
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<para>The actual locations assigned to uniform variables are not
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known until the program object is linked successfully. After
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linking has occurred, the command
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<function>glGetUniformLocation</function> can be used to obtain
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the location of a uniform variable. This location value can then
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be passed to
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<citerefentry><refentrytitle>glUniform</refentrytitle></citerefentry>
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to set the value of the uniform variable or to
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<citerefentry><refentrytitle>glGetUniform</refentrytitle></citerefentry>
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in order to query the current value of the uniform variable.
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After a program object has been linked successfully, the index
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values for uniform variables remain fixed until the next link
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command occurs. Uniform variable locations and values can only
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be queried after a link if the link was successful.</para>
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</refsect1>
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<refsect1 id="errors"><title>Errors</title>
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<para><constant>GL_INVALID_VALUE</constant> is generated if
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<parameter>program</parameter> is not a value generated by
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OpenGL.</para>
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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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<parameter>program</parameter> is not a program object.</para>
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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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<parameter>program</parameter> has not been successfully
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linked.</para>
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</refsect1>
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<refsect1 id="associatedgets"><title>Associated Gets</title>
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<para><citerefentry><refentrytitle>glGetActiveUniform</refentrytitle></citerefentry>
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with arguments <parameter>program</parameter> and the index of
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an active uniform variable</para>
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<para><citerefentry><refentrytitle>glGetProgram</refentrytitle></citerefentry>
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with arguments <parameter>program</parameter> and
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<constant>GL_ACTIVE_UNIFORMS</constant> or
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<constant>GL_ACTIVE_UNIFORM_MAX_LENGTH</constant></para>
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<para><citerefentry><refentrytitle>glGetUniform</refentrytitle></citerefentry>
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with arguments <parameter>program</parameter> and the name of a
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uniform variable</para>
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<para><citerefentry><refentrytitle>glIsProgram</refentrytitle></citerefentry></para>
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</refsect1>
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<refsect1 id="seealso"><title>See Also</title>
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<para><citerefentry><refentrytitle>glLinkProgram</refentrytitle></citerefentry>,
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<citerefentry><refentrytitle>glUniform</refentrytitle></citerefentry></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> 2003-2005 3Dlabs Inc. Ltd.
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This material may be distributed subject to the terms and conditions set forth in
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the Open Publication License, v 1.0, 8 June 1999.
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<ulink url="http://opencontent.org/openpub/">http://opencontent.org/openpub/</ulink>.
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</para>
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</refsect1>
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</refentry>
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