[Soc-2016-dev] Weekly Report #12 - Cycles Denoising

[Sergey Sharybin]

Hi,

When you mention using intrinsics to speed something up it's always
interesting to know what kind of speedup this gives.

Also while blue noise is an interesting experiment, it's not a part of GSoC
so not sure what it is doing in the report.

In Blender we use threaded EXR decoding, so that could be a reason why OIIO
is poor in performance. It had some options for threading AFAIR, so make
sure the IO is threaded there.

On Sat, Aug 13, 2016 at 5:47 AM, Lukas Stockner <lukas.stockner at freenet.de>
wrote:

> Hi!
>
> This week, I started over the weekend by doing some minor changes and
> fixes:
>  - Now, Cycles Standalone has a command line option to set the tile size
> (ffea3f5a in the branch, ef27d8ec in master)
>  - Revert a "fix" that actually totally broke Glossy/Glass GGX (10cb9a19)
>  - Fix building after the debug_fpe commit (edcf60b4)
>  - Fix a wrong calculation of the feature matrix norm (d23f0003)
>  - Remove some useless files I added a while back by accident
>  - Moving denoise utility and prefiltering functions into separate files
> to clean up the main file (b7dc25cb)
>
> The next larger feature was standalone denoising of single frames: By
> rendering with denoising information enabled (no need to activate denoising
> itself) and saving the result as Multilayer EXR, that EXR can then be
> denoised by Cycles Standalone to produce a clean output file. In itself,
> that feature is mainly useful for development, since it allows to
> pre-render once and just test the filter. (Commit: 3f94371a)
>
> After that, I decided to go for the SIMD kernel optimization next. That
> resulted in:
>  - A fix for a pretty longstanding hidden issue in master, where SSE4.1
> function fallbacks were accidentally also used to override the native
> functions (cf017e81)
>  - A few SSE utility functions, like horizontal maximum and sum (741a2453)
>  - A SSE4.1-optimized version of the first kernel, which used to take up
> most of the time. The speedup in that function depends on a few factors,
> but it's usually about 2-3 times faster (dba99c49).
>  - A SSE4.1-optimized version of the NLM prefiltering kernel, which
> reduces prefiltering time by a factor of about 3 (95fa4836)
> Together, these functions make denoising more than twice as fast on
> compatible processors (pretty much any processor since 2011).
>
> Next, I created a clean implementation of the Blue-Noise dithering patch -
> now under review at D2149. While doing so, I also fixed a problem in master
> regarding CUDA texture limits (bbbc079a), fixed the KernelIntegrator
> structure padding that was wrong since the Light Portal commit (82e65abf)
> and added a CTest that checks for problems like that in the future
> (7c3a06c3).
>
> One of the components of D2149, the simulated annealing tool used to
> precalculate the dither matrix, took a bit of time to optimize - but after
> a number of improvements, such as approximate math functions and yet
> another SSE4.1-optimized code path, it now runs 9 times as fast! A
> simulation pass with 3 Billion iterations is running right now, I'll upload
> the result once it's done.
>
> After that, I finished the standalone denoising by finally adding the
> inter-frame denoising mode (1c675f1c, e0208200, 2af90268) - now, the
> denoiser can use previous and later frames to avoid flickering and produce
> a better result in general!
> The filtering is a bit slow, though - one reason for that is that OIIO
> actually needs about 10 seconds to read five Multilayer EXRs from the disk,
> and I don't yet understand why (Disk I/O isn't the bottleneck, I even tried
> a Ramdisk). Also, it's just more pixels - but that could be improved by
> doing things like using a smaller half window for secondary frames.
>
>
>
> So, since next week is the final GSoC week, I'll spend most of my time on
> final documentation.
> The project in general is in a working shape now, I covered the main parts
> of the proposal (except for possibly adaptive sampling), but the branch
> isn't close to being finished and polished yet.
>
> Of course, though, I'll continue to work on it after the GSoC ends - my
> goal is to get the denoiser into master, after all!
>
> Lukas
>
>
> _______________________________________________
> Soc-2016-dev mailing list
> Soc-2016-dev at blender.org
> https://lists.blender.org/mailman/listinfo/soc-2016-dev
>
>


-- 
With best regards, Sergey Sharybin
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.blender.org/pipermail/soc-2016-dev/attachments/20160815/14105629/attachment.htm