[Bf-committers] Couple of questions about rendering settings using python scripts and strange GPU performance

Andrey Chursin andll at danasoft.ws
Fri Apr 24 19:09:07 CEST 2015


Ooops, sorry for that. I've posted other questions to forum you've provided.
Thanks for reply about tiles

2015-04-24 9:30 GMT-07:00 Marc Dion <marcdion1974 at gmail.com>:
> So far as I understand it, the tile size is only used to format the data
> into chunks which better match an individual computer's capabilities.
>
> There should be no change in quality.  If there is a difference in the
> final results, this would be a good reason to file a bug report on the
> tracker.   https://developer.blender.org/
> ---
>
> A better place for questions like this may be
>
> *http://blender.stackexchange.com/questions
> <http://blender.stackexchange.com/questions>*
> Other people starting out will want to know things like this and Blender
> Stack Exchange answers will be easier for them to locate.
>
> I think this list is supposed to be for programmers to discuss changes to
> Blender's source code :)
>
> On Fri, Apr 24, 2015 at 8:47 AM, Andrey Chursin <andll at danasoft.ws> wrote:
>
>> Thanks for fast response!
>>
>> As I understand, tiles size only affects performance (+memory usage)
>> and may be preview generation, but does not affect quality of result?
>> So basically, does adjusting of tiles size impact finally rendered
>> image?
>>
>> 2015-04-23 22:39 GMT-07:00 gandalf3 <zzyxpaw at gmail.com>:
>> > Regarding CPU vs GPU, tile size plays a big role. As a general rule of
>> > thumb, CPUs like smaller tile sizes and  GPUs like larger tile sizes.
>> > It varies from GPU to GPU and from scene to scene, but I tend to use a
>> > tile size of about 128 for my gpu.
>> >
>> > On 04/23/15 22:36, Andrey Chursin wrote:
>> >> Hi
>> >>
>> >> I am processing blender file using python script passed in -P cmd
>> argument
>> >>
>> >> I am new to blender so I am not familiar with all bpy
>> >> objects/properties. Can you help me with it?
>> >>
>> >> 1) How can I get current rendering tile and estimated time in cycles
>> >> rendering engine? I know there is render_stats handler, and I even
>> >> found function BlenderSession::get_progress in sources, but I am still
>> >> puzzled how can I get this info from python script.
>> >> 2) How can I get list of cameras available?
>> >> 3) How can I setup active camera for rendering?
>> >> 4) How can I get/set number of samples when rendering?
>> >>
>> >> And some question about GPU performance
>> >>
>> >> I was rendering first frame from classroom from blender demo
>> >> (
>> http://www.blender.org/wp-content/uploads/2015/04/classroom-200x107.png)
>> >>
>> >> I tested it on c4.large AWS virtual machine (2 cores of Intel Xeon
>> >> E5-2666 v3) vs g2.8xlarge GPU vm(4 unspecified nvidia GPUs with 1,536
>> >> CUDA cores each)
>> >>
>> >> What puzzles me is that 2-core CPU vm renders 2x faster then 4-GPUs
>> machine.
>> >>
>> >> On GPU I was using combined cuda device, and all GPUs was actually
>> >> busy(nvidia-smi shows 99% utilization of all 4 GPUs)
>> >>
>> >> I understand that GPU/CPU are not very comparable, but results are
>> >> still strange. Is there any specific conditions when GPU actually
>> >> works faster then CPU?
>> >>
>> >>
>> >
>> >
>> > --
>> > -gandalf3
>> >
>> > _______________________________________________
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>> > Bf-committers at blender.org
>> > http://lists.blender.org/mailman/listinfo/bf-committers
>>
>>
>>
>> --
>> Regards,
>> Andrey
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-- 
Regards,
Andrey


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