[Bf-cycles] Tiles sizes - impact on RAM and speed

[Ole Jakob Skjelten]

Thanks a lot Brecht - this answer the last of my questions, I'll incorporate into the FAQ and do my best to make sure people know :)


OJ

--
Ole Jakob Skjelten
olesk at pvv.org
+41 79 832 2976




On 10. feb. 2013, at 18:45, Brecht Van Lommel <brechtvanlommel at pandora.be> wrote:

> On Sun, Feb 10, 2013 at 5:52 PM, Ole Jakob Skjelten <olesk at pvv.org> wrote:
>> Thanks a lot for that Brecht! My understanding is that *reducing* tile sizes
>> only has a positive effect with regards to reducing the size of the output
>> buffer, which is in most cases is a rather small part of the total RAM eaten
>> by Cycles, and thus, unless you you're in a desperate
>> I-only-need-10MB-more-RAM-to-render-on-my-GPU scenario, increasing the tile
>> size for speed benefits is the more likely scenario. Would you agree?
> 
> Yes, I agree. Maybe if you have a ton of render passes, but otherwise
> you can quite safely set it quite large.
> 
>> It's also my understanding that, using CUDA, keeping your tiles to multiples
>> of 16 pixels helps speed (or rather prevent wasting GPU cycles)? And
>> finally, does it help to operate with tiles that are multiples of the full
>> render resolution, or should one use same values for x and y direction
>> (square tiles) instead?
> 
> Multiples of 16 might indeed help, I'm not quite sure if this true in
> general though and if this perhaps depends on the particular GPU.
> Multiples of the render resolution will help if you use big tiles,
> since otherwise you can get some smaller tiles to fill up the full
> render.
> 
> Brecht.
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