NAME

       cl_khr_gl_event - Create an OpenCL event object from a GL sync object.

       cl_khr_gl_event

DESCRIPTION

       This extension enables the function clCreateEventFromGLsyncKHR(3clc).

       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 GL_ARB_cl_event
       OpenGL extension provides the complementary functionality of creating an OpenGL sync object from an
       OpenCL event object.

       In addition, this extension modifies the behavior of clEnqueueAcquireGLObjects(3clc) and
       clEnqueueReleaseGLObjects(3clc) to implicitly guarantee synchronization with an OpenGL context bound in
       the same thread as the OpenCL context.

       If this extension is supported by an implementation, the string cl_khr_gl_event will be present in the
       CL_PLATFORM_EXTENSIONS or CL_DEVICE_EXTENSIONS string described in the table of param_name values for
       clGetDeviceInfo(3clc).

NOTES

       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).

       If the cl_khr_gl_event 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.

       If the cl_khr_gl_event 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 glFenceSync, creating an event from the resulting GL sync object using
       clCreateEventFromGLsyncKHR(3clc), and determining completion of that event object via
       clEnqueueAcquireGLObjects(3clc). This method may be considerably more efficient than calling glFinish,
       and is referred to as explicit synchronization. Explicit synchronization is most useful when an OpenGL
       context bound to another thread is accessing the memory objects.

       If the cl_khr_gl_event extension is not supported, completion of OpenGL commands may be determined by
       issuing and waiting for completion of a glFinish 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.

       Note that no synchronization method other than glFinish 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, glFinish is an expensive operation and its use should be avoided if the cl_khr_gl_event
       extension is supported on a platform.

SPECIFICATION

       OpenCL Specification[1]

SEE ALSO

       EXTENSION(3clc), clCreateEventFromGLsyncKHR(3clc)

AUTHORS

       The Khronos Group

COPYRIGHT

       Copyright © 2007-2011 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.

NOTES

        1. OpenCL Specification
           page 61, section 9.8 - Creating CL event objets

The Khronos Group                                  01/14/2021                              CL_KHR_GL_EVENT(3clc)