Non Omnis Moriar - OpenGL + OpenCL vs. DirectX11

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OpenGL + OpenCL vs. DirectX11

OpenGL + OpenCL vs. DirectX11	Jan. 8th, 2009 @ 03:20 pm

"OpenCL does bring an interesting element to the table. One of the major advancements of DirectX 11 will be the addition of a compute shader to the pipeline. This compute shader will be general purpose and capable of operating on diverse data structures that pixel shaders are not geared towards. It will be capable of things like OpenCL is, though it will be tuned and geared toward doing so in the context of graphics. It is, after all, still DirectX. In DX11, the pixel shader and compute shader will share data via data structures rather than any sort of formal input/output mechanism. Because of the high level of integration, game developers (and other graphics engine developers) will be capable of tightly combining current techniques with more general purpose code that can handle a broader array of algorithms.

OpenGL doesn't have anything like this in the works, but OpenCL fixes that. OpenCL is capable of sharing data with OpenGL. And we aren't talking about copying data back and forth easily, we are talking about physically sharing data structures and memory locations. This essentially adds a compute shader to OpenGL for those who want it. Why is that the case? well, offering OpenCL users a means of using OpenGL images and buffers as OpenCL images and buffers means that OpenGL and OpenCL can share data with no copy or conversion overhead. This means that not only are OpenGL and OpenCL able to work on the same data, but that the method by which they communicate is very similar to what DX11 does to allow the passing of data between pixel an geometry shaders.

While game developers may be intrigued, the professional app developers may have more of a reason to get excited. Sure, this will allow OpenGL game developers to use a compute shader like option, but it gives professional application developers the ability to actually combine the real work of simulation or data manipulation with visualization. With support for double precision in hardware that supports it, this could be useful for applications where a lot of real work needs to be done both on the thing being visualized and the visualization itself. This could speed things up quite a bit and allow fluid realtime visualization and manipulation of much more complicated data sets.

Additionally, this compute shader will work on hardware not specifically designed as DX11 class hardware. DX11, as a strict superset of DX10, will extend some functionality to DX10 hardware, but we aren't yet certain about the specifics of this and it may include CS functionality. On top of this, OpenCL should get drivers in the first quarter of next year. This puts the combination of OpenGL 3.0 plus OpenCL 1.0, for the first time in a long time, ahead of DirectX in terms of technology and capability. This is by no means a result of the sluggish and non-innovative OpenGL ARB. But maybe this will inspire more use of OpenGL, which maybe will inspire more innovation from the ARB. But I'm not going to hold my breath on that one." ~ Anand

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