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

[Marc Dion]

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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>
>
> --
> Regards,
> Andrey
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