145 lines
6.2 KiB
XML
145 lines
6.2 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="glGetUniform">
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<refmeta>
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<refentrytitle>glGetUniform</refentrytitle>
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<manvolnum>3G</manvolnum>
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</refmeta>
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<refnamediv>
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<refdescriptor>glGetUniform</refdescriptor>
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<refname>glGetUniformfv</refname>
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<refname>glGetUniformiv</refname>
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<refpurpose>Returns the value 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>void <function>glGetUniformfv</function></funcdef>
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<paramdef>GLuint <parameter>program</parameter></paramdef>
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<paramdef>GLint <parameter>location</parameter></paramdef>
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<paramdef>GLfloat *<parameter>params</parameter></paramdef>
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</funcprototype>
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<funcprototype>
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<funcdef>void <function>glGetUniformiv</function></funcdef>
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<paramdef>GLuint <parameter>program</parameter></paramdef>
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<paramdef>GLint <parameter>location</parameter></paramdef>
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<paramdef>GLint *<parameter>params</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>location</parameter></term>
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<listitem>
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<para>Specifies the location of the uniform variable
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to be queried.</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>params</parameter></term>
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<listitem>
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<para>Returns the value of the specified uniform
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variable.</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>glGetUniform</function> returns in
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<parameter>params</parameter> the value(s) of the specified
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uniform variable. The type of the uniform variable specified by
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<parameter>location</parameter> determines the number of values
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returned. If the uniform variable is defined in the shader as a
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boolean, int, or float, a single value will be returned. If it
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is defined as a vec2, ivec2, or bvec2, two values will be
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returned. If it is defined as a vec3, ivec3, or bvec3, three
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values will be returned, and so on. To query values stored in
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uniform variables declared as arrays, call
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<function>glGetUniform</function> for each element of the array.
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To query values stored in uniform variables declared as
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structures, call <function>glGetUniform</function> for each
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field in the structure. The values for uniform variables
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declared as a matrix will be returned in column major
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order.</para>
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<para>The locations assigned to uniform variables are not known
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until the program object is linked. After linking has occurred,
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the command
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<citerefentry><refentrytitle>glGetUniformLocation</refentrytitle></citerefentry>
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can be used to obtain the location of a uniform variable. This
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location value can then be passed to
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<function>glGetUniform</function> in order to query the current
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value of the uniform variable. After a program object has been
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linked successfully, the index values for uniform variables
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remain fixed until the next link command occurs. The uniform
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variable values can only be queried after a link if the link was
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successful.</para>
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</refsect1>
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<refsect1 id="notes"><title>Notes</title>
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<para><function>glGetUniform</function> is available only if the
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GL version is 2.0 or greater.</para>
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<para>If an error is generated, no change is made to the
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contents of <parameter>params</parameter>.</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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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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<parameter>location</parameter> does not correspond to a valid
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uniform variable location for the specified program object.</para>
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<para><constant>GL_INVALID_OPERATION</constant> is generated if
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<function>glGetUniform</function> is executed between the
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execution of
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<citerefentry><refentrytitle>glBegin</refentrytitle></citerefentry>
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and the corresponding execution of
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<citerefentry><refentrytitle>glEnd</refentrytitle></citerefentry>.</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 an active
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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>glGetUniformLocation</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>glCreateProgram</refentrytitle></citerefentry>,
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<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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