sdk/2.1/docs/man/cl_khr_gl_event.xml

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    <refentryinfo>
        <keywordset>
            <keyword>cl_khr_gl_event</keyword>
        </keywordset>
    </refentryinfo>

    <refmeta>
        <refentrytitle>cl_khr_gl_event</refentrytitle>

        <refmiscinfo>
            <copyright>
                <year>2007-2013</year>
                <holder>The Khronos Group Inc.
 Permission is hereby granted, free of charge, to any person obtaining a
copy of this software and/or associated documentation files (the
"Materials"), to deal in the Materials without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Materials, and to
permit persons to whom the Materials are furnished to do so, subject to
the condition that this copyright notice and permission notice shall be included
in all copies or substantial portions of the Materials.</holder>
            </copyright>
        </refmiscinfo>
        <manvolnum>3</manvolnum>
    </refmeta>

<!-- ================================ SYNOPSIS -->

    <refnamediv id="cl_khr_gl_event">
        <refname>cl_khr_gl_event</refname>

        <refpurpose>
            Create an OpenCL event object from a GL sync object.
        </refpurpose>
    </refnamediv>


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cl_khr_gl_event
                        </entry>
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<!-- ================================ DESCRIPTION  -->


    <refsect1 xmlns:xlink="http://www.w3.org/1999/xlink" id="description"><title>Description</title>
        <para>
            This extension enables the function 
            <citerefentry><refentrytitle>clCreateEventFromGLsyncKHR</refentrytitle></citerefentry>.
        </para>

        <para>
            This extension allows creating OpenCL event objects linked to OpenGL fence sync objects,
            potentially improving efficiency of sharing images and buffers between the two APIs. The
            companion <function>GL_ARB_cl_event</function> OpenGL extension provides the
            complementary functionality of creating an OpenGL sync object from an OpenCL event object.
        </para>

        <para>
            In addition, this extension modifies the behavior of 
            <citerefentry><refentrytitle>clEnqueueAcquireGLObjects</refentrytitle></citerefentry>
            and <citerefentry><refentrytitle>clEnqueueReleaseGLObjects</refentrytitle></citerefentry>
            to implicitly guarantee synchronization with an OpenGL context bound 
            in the same thread as the OpenCL context.
        </para>

        <para>
            If this extension is supported by an implementation, the 
            string <function>cl_khr_gl_event</function>
            will be present in the <constant>CL_PLATFORM_EXTENSIONS</constant> 
            (see <citerefentry><refentrytitle>clGetPlatformInfo</refentrytitle></citerefentry>) 
            or <constant>CL_DEVICE_EXTENSIONS</constant> string 
            (see <citerefentry><refentrytitle>clGetDeviceInfo</refentrytitle></citerefentry>).
        </para>
    </refsect1>


<!-- ================================ NOTES  -->


    <refsect1 xmlns:xlink="http://www.w3.org/1999/xlink" id="notes"><title>Notes</title>

     <para>
        Event objects can also be used to reflect the 
        status of an OpenGL sync object. The sync object
        in turn refers to a fence command executing 
        in an OpenGL command stream. This provides
        another method of coordinating sharing of 
        buffers and images between OpenGL and OpenCL
        (see section 9.7.6.1).
        </para>

        <para>
            If the <function>cl_khr_gl_event</function> extension is supported, 
            then the OpenCL implementation will ensure that
            any such pending OpenGL operations are complete 
            for an OpenGL context bound to the same
            thread as the OpenCL context. This is referred 
            to as implicit synchronization.
        </para>

        <para>
            If the <function>cl_khr_gl_event</function> extension is 
            supported and the OpenGL context in question supports
            fence sync objects, completion of OpenGL commands may also 
            be determined by placing a GL fence command after
            those commands using <function>glFenceSync</function>, 
            creating an event from the resulting GL sync object using 
            <citerefentry><refentrytitle>clCreateEventFromGLsyncKHR</refentrytitle></citerefentry>, 
            and determining completion of that event object via 
            <citerefentry><refentrytitle>clEnqueueAcquireGLObjects</refentrytitle></citerefentry>. 
            This method may be considerably more efficient than calling 
            <function>glFinish</function>, and is referred to as
            <varname>explicit synchronization</varname>. Explicit 
            synchronization is most useful when an OpenGL context
            bound to another thread is accessing the memory objects.
        </para>

        <para>
            If the <function>cl_khr_gl_event</function> extension 
            is not supported, completion of OpenGL commands may be
            determined by issuing and waiting for completion of a 
            <function>glFinish</function> command on all OpenGL
            contexts with pending references to these objects. Some 
            implementations may offer other efficient synchronization
            methods. If such methods exist they will be described 
            in platform-specific documentation.
        </para>

        <para>
            Note that no synchronization method other than 
            <function>glFinish</function> is portable between all OpenGL
            implementations and all OpenCL implementations. 
            While this is the only way to ensure completion that is portable
            to all platforms, <function>glFinish</function> is 
            an expensive operation and its use should be avoided if the
            <function>cl_khr_gl_event</function> extension is supported on a platform.
        </para>
    </refsect1>


<!-- ================================ EXAMPLE  -->
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<!-- ================================ SPECIFICATION  -->
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            <olink uri="cl_khr_gl_event">OpenCL Specification</olink>
        </para>
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<!-- ================================ ALSO SEE -->

    <refsect1 id="seealso"><title>Also see</title>
        <para>
            <citerefentry><refentrytitle>EXTENSION</refentrytitle></citerefentry>,
            <citerefentry><refentrytitle>clCreateEventFromGLsyncKHR</refentrytitle></citerefentry>
        </para>
    </refsect1>


<!-- ============================== COPYRIGHT -->
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<!-- 21-Dec-2013, rev. 19 -->
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