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

[Andrey Chursin]

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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-- 
Regards,
Andrey