[Bf-committers] Proposal: Blender OpenCL compositor

Jeroen Bakker j.bakker at atmind.nl
Sat Jan 15 09:07:17 CET 2011



On 01/15/2011 08:19 AM, Matt Ebb wrote:
> Thanks, Jeroen.
>
> On Sat, Jan 15, 2011 at 6:04 PM, Jeroen Bakker<j.bakker at atmind.nl>  wrote:
> Farms
>> are already being migrated to OpenCL farms. As they are cheaper in
>> hardware costs.
>>
>> BTW. renderfarm.fi should be capable of running OpenCL as this is
>> proposal is implemented!
> While I can believe that there will be dedicated online farms set up
> for this sort of thing I was more referring to farms in animation
> studios, most of which are not designed around GPU power - now, and
> nor probably for a while in the future. Even imagining if in the
> future blender uses openCL heavily, if a studio has not designed a
> farm specifically for blender (which is quite rare), CPU performance
> will continue to be very important. I'm curious how openCL translates
> to CPU multiprocessing performance, especially in comparison with
> using something like blender's existing pthread wrapper.
Thanks for your insight. If you only have OpenCL for CPU (AMD, Intel) it 
is hard to determine the results.
1. The OpenCL code is compiled to native code and executed as a shared 
library. The code itself should run without speed loss.
2. You have the overhead of the task scheduler in the OpenCL driver. -> 
Speed decreases
3. You can utilize your hardware better -> increase of speed.

If you compare non OpenCL CPU with OpenCL CPU, you really can't say 
anything about which one is faster, because your comparing two different 
styles and implementations. It depends on the actual implementation that 
you will test.

Currently AMD has better support for openCL, but in the short future 
Intel will be up to speed.
Also bullet physics engine 3.x will uses OpenCL and as most studios have 
bullet somewhere... Still I have not yet tested it.

Jeroen


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