[Bf-cycles] Optimization project

[Brecht Van Lommel]

It depends on what you mean exactly by this penalty. For Cycles the
path tracer and branched path tracer work different. In the former
cases it will pick one of the layers at random for each AA sample, in
the latter case it will do all layers for each AA sample. So for the
branched path tracer there is a higher cost but also less noise per AA
sample.

So it's not clear to me if you are talking about total render time to
achieve some level of noise, or time per AA sample. If Arnold only
gives a slight speed hit but more noise then I guess it does what we
do in the non-branched path tracer. There's some tradeoffs between the
two ways.

It may be something else in the importance sampling that needs work if
it's more about noise / render time.

On Sun, Feb 9, 2014 at 10:43 PM, Matthew Heimlich
<matt.heimlich at gmail.com> wrote:
> Not sure at all how it's done, but it might be a good jumping off
> place to think from: In Cycles, you get a huge penalty every time you
> add another layer to SSS, while in Arnold working with six layers of
> SSS gives only a slight speed hit over using just one. Any thoughts?
>
> On Sun, Feb 9, 2014 at 4:02 PM, Daniel Salazar - patazstudio.com
> <zanqdo at gmail.com> wrote:
>> Ok, I will very soon provide you with WIP scenes, at least to understand why
>> it is so scary slow :)
>>
>> Daniel Salazar
>> patazstudio.com
>>
>>
>> On Sun, Feb 9, 2014 at 2:59 PM, Brecht Van Lommel
>> <brechtvanlommel at pandora.be> wrote:
>>>
>>> I don't have any great ideas to improve raytraced SSS performance,
>>> there's two tweaks we can do on the list now and general BVH
>>> performance improvements should help also. There's probably more we
>>> can do but I'm not sure what at the moment, analysis of some real
>>> world scenes should reveal some ways that it can be improved.
>>>
>>> On Sun, Feb 9, 2014 at 8:33 PM, Daniel Salazar - patazstudio.com
>>> <zanqdo at gmail.com> wrote:
>>> > We are using SSS for our very simple part of the teaser. A single
>>> > character
>>> > on outdoors lighting. Its surprising how much of a speed penalty there
>>> > is
>>> > with SSS :p Of course for a few seconds in the teaser it's alright  but
>>> > I'm
>>> > foreseeing our project will be an SSS and hair frenzy!! :D
>>> >
>>> > On Feb 9, 2014 12:00 PM, "Marco G" <digitalbath86 at hotmail.com> wrote:
>>> >>
>>> >> Hi,
>>> >> about hair, haven't seen any specific paper link to help shading and
>>> >> rendering speedup.
>>> >>
>>> >> Is there anything already implemented so far, or other ideas?
>>> >> Reading at the pdf, the recent Importance sampling from Marschner et
>>> >> al,
>>> >> could be used in conjunction with Dual scattering,
>>> >> i remember reading in this mailing list, people willing to integrate
>>> >> dual
>>> >> scattering.
>>> >>
>>> >> Dual scattering -
>>> >> http://www.cemyuksel.com/research/dualscattering/dualscattering.pdf
>>> >>
>>> >> Importance sampling -
>>> >> http://cg.ibds.kit.edu/publications/pubhanika/2013_hairbrief.pdf
>>> >>
>>> >> A quote from the paper:
>>> >>
>>> >> "Our sampling scheme can be used for direct illumination sampling
>>> >> (where indirect illumination may be approximated by Dual Scattering
>>> >> [Zinke et al. 2008]) and also for indirect illumination, where
>>> >> sampling at each vertex of a random path is used to create photon
>>> >> maps within hair volumes [Moon et al. 2008] or within a variety
>>> >> of unbiased path-tracing algorithms"
>>> >>
>>> >> Thoughts?
>>> >>
>>> >> MG
>>> >>
>>> >>
>>> >> > From: brechtvanlommel at pandora.be
>>> >> > Date: Wed, 5 Feb 2014 17:02:11 +0100
>>> >> > To: bf-cycles at blender.org
>>> >> > Subject: [Bf-cycles] Optimization project
>>> >> >
>>> >> > Hi all,
>>> >> >
>>> >> > With Gooseberry coming up, it would be good to start focusing on
>>> >> > (CPU)
>>> >> > optimization for the next few release cycles. For new features I
>>> >> > still
>>> >> > plan to finish volume rendering and add deformation motion blur soon,
>>> >> > but besides that a more organized optimization project is something
>>> >> > I'd like to spend time on.
>>> >> >
>>> >> > See this wiki page for more details:
>>> >> >
>>> >> >
>>> >> > http://wiki.blender.org/index.php/Dev:2.6/Source/Render/Cycles/Optimization
>>> >> >
>>> >> > There's already great work being done by Sv. Lockal and others in
>>> >> > this
>>> >> > area, on the low level optimization front, but there's many more
>>> >> > opportunities. I'll try to add more detail and ideas over time, this
>>> >> > is just what I could think of off the top of my head.
>>> >> >
>>> >> > You can help out in various ways:
>>> >> > * Contribute code to implement optimizations
>>> >> > * Help gathering of test scenes representative of Gooseberry shots
>>> >> > * Suggest practical optimizations ideas
>>> >> >
>>> >> > It would also be cool if someone could set up some webpage with a
>>> >> > graph that tracks Cycles performance on test scenes over time, maybe
>>> >> > doing a render with the latest Git version once a week or so (like
>>> >> > http://arewefastyet.com/).
>>> >> >
>>> >> > Thanks,
>>> >> > Brecht.
>>> >> > _______________________________________________
>>> >> > Bf-cycles mailing list
>>> >> > Bf-cycles at blender.org
>>> >> > http://lists.blender.org/mailman/listinfo/bf-cycles
>>> >>
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>>> >>
>>> >
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>>
>>
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