[Bf-cycles] CUDA Toolkit 6.5 and Volume on GPU

Sergey Sharybin sergey.vfx at gmail.com
Fri Aug 22 16:17:49 CEST 2014

Thanks for the tests, just wanted to add small note about time comparisons.
You really need to do much longer renders, which takes several minutes at

28.07 vs. 28.25 doesn't mean all the renderers are 1% slower, it might be
just a time constant, which needs to start the bigger kernel, which you
wouldn't really notice if your render time is some minutes at least. Also
such a small time differences might be caused by factors like different
timing of scheduling blender in the OS task scheduler caused by
interference with other running processes and so.

That would make timing more accurate.

Textures might do rendering slower yes, could be optimized perhaps on GPU,
but for me doesn't seem to be a stopper for enabling volumes on GPU.

On Fri, Aug 22, 2014 at 8:06 PM, David Fenner <d4vidfenner at gmail.com> wrote:

> Ok, done some further testing and the thing that really kills gpu
> performance are textures in volumes. With no textures gtx Titan is about 3
> times faster than a 6-core overclocked ivy bridge, even with volume scatter
> and lots of bounces. However when textures are introduced, amazingly cpu
> gets about 1.5 times faster than gpu. That means that texturing volumes
> cripples gpu performance by about 4 times.  Still, non textured volumes are
> actually flying on the gpu (even though its only distance sampling) and are
> totally worth it for now.
> 2014-08-22 9:57 GMT-04:00 David Fenner <d4vidfenner at gmail.com>:
> On GTX titan, mike pan test:
>> 2.71 official                  27.62
>> vainilla cuda 6.5          28.07
>> volume cuda 6.5          28.25
>> Notes: Was testing volumes and with a simple world volume and a lamp now
>> it's actually much faster than cpu (before gpu was crazy slow). Haven't
>> tested it with more complex scenes.  I noticed though that in gpu volume
>> gets always sampled as "distance" sampling, no matter the setting. Cpu
>> however respects the other settings (equiangular, etc). In distance gpu
>> much faster and its also faster when bounces are introduced, something that
>> in older builds really killed gpu performance.
>> 2014-08-22 8:48 GMT-04:00 Tungerz <tungerz at gmail.com>:
>>> Probably nothing,
>>> I was upgrading my Cuda Toolkit to 6.5 (From 6.0)
>>> My Norton antivirus picked up a virus from file nppc32_65.dll =
>>> Suspicious.Cloud.7.F
>>> Anyone else on windows had this?
>>> Great results, looks like a small price to pay for gpu volume and
>>> scatter.
>>> Worth ever bit of it :)
>>> Cheers,
>>>  ~Tung
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>>> Bf-cycles at blender.org
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With best regards, Sergey Sharybin
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