[Bf-cycles] max bounces

[Daniel Salazar - patazstudio.com]

Thank you, that clears things up!
Daniel Salazar
patazstudio.com


On Thu, Nov 6, 2014 at 3:45 PM, Brecht Van Lommel
<brechtvanlommel at pandora.be> wrote:
> If you render with 1 for min bounces that explains the timings. If the
> min bounces is smaller than the max bounces, that enables Russian
> roulette path termination. This means most paths will be terminated
> early and not use the max bounces, when Cycles detects that they
> contribute little to the image.
>
> For the same reason 200 bounces is not that slow, since only very few
> paths will actually use that many bounces. Even if min bounces is set
> to 200, the path will probably escape to the sky or hit enough dark
> surfaces that the contribution becomes too small to matter.
>
> On Thu, Nov 6, 2014 at 10:12 PM, Daniel Salazar - patazstudio.com
> <zanqdo at gmail.com> wrote:
>> I've also found strange how you can make cycles calculate 200 bounces
>> with not much apparent slowdown, wonder why..
>> Daniel Salazar
>> patazstudio.com
>>
>>
>> On Thu, Nov 6, 2014 at 2:42 PM, David Fenner <d4vidfenner at gmail.com> wrote:
>>> Hi Thomas, thanks for the reply. I'll try to find time todar or tomorrow at
>>> most to do a more clear test, with pics and blend file. I'm pretty sure I
>>> tested it with 1 min bounce all the time though, but I'll run them again and
>>> upload in a more organized way.
>>>
>>> Thanks again,
>>> David.
>>>
>>> 2014-11-06 17:37 GMT-03:00 E. David Ferriman <dferriman at gmail.com>:
>>>
>>>> Awesome! Thanks!
>>>>
>>>> On 11/6/2014 3:33 PM, Thomas Dinges wrote:
>>>>
>>>> Hi David,
>>>> that is weird, I cannot think of a reason for this at the moment.
>>>>
>>>> The way the feature works, is that it checks if the Light Max Bounce
>>>> setting is greater than the current bounce, if that's the case it skips
>>>> evaluating the lamp.
>>>> Did you use the Pathtrace or Branched Pathtrace integrator? Also what were
>>>> your global min bounces? If they differed from the global max bounces, it
>>>> might be worth to check again with these 2 values being the same.
>>>>
>>>> Thomas
>>>>
>>>> Am 06.11.2014 um 14:00 schrieb David Fenner:
>>>>
>>>> Hi Thomas, thanks for the commit yesterday, to control bounces per light,
>>>> very nice!!
>>>>
>>>> Been doing some tests here, and I ran into a very strange scenario:
>>>>
>>>> When I have 3 or more max diffuse bounces in global render settings,
>>>> reducing per lamp bounces have little to no impact in render times, even if
>>>> set to 0 bounces. However, when I have only 2 max diffuse bounces in render
>>>> settings, lowering per lamp bounces have a very big impact on render times,
>>>> reducing them almost as much as if I lowered global diffuse bounces on the
>>>> same quantity. It's like there was some sort of threshold at 2 global
>>>> bounces. For example:
>>>>
>>>> (on a simple diff scene with one lamp)
>>>>
>>>>
>>>> Global Max Diff Bounces = 0
>>>> Lamp bounces                 = 0
>>>> Render Time: 4.7 sec
>>>>
>>>>
>>>> Global Max Diff Bounces = 3
>>>> Lamp bounces                 = 1024
>>>> Render Time: 10 sec
>>>>
>>>>
>>>> Global Max Diff Bounces = 3
>>>> Lamp bounces                 = 0
>>>> Render Time: 9.7 sec   (almost the same as before)
>>>>
>>>>
>>>> Global Max Diff Bounces = 2
>>>> Lamp bounces                 = 2
>>>> Render Time: 8.5 sec      (lower rendertime thanks to one less bounce)
>>>>
>>>>
>>>> Global Max Diff Bounces = 2
>>>> Lamp bounces                 = 0
>>>> Render Time: 4.9 sec       (before it didn't even care, yet for 2 bounces
>>>> and below its almost as there where no global bounces)
>>>>
>>>>
>>>> It's great, with 2 global diff bounces and below the gains of lowering per
>>>> lamp bounces are almost as big as if lowering global diffuse bounces, so
>>>> having only a few lights with GI can increase your rendertimes amazingly,
>>>> however,  with 3 global diff bounces and over there is strangely almost no
>>>> gain, even when all lamps have 0 bounces.
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
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>>>>
>>>>
>>>>
>>>>
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>>>>
>>>> --
>>>> E. David Ferriman
>>>> Web Designer
>>>> dferriman,com
>>>> dferriman at gmail.com | (614) 260-7238
>>>>
>>>>
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>>>
>>>
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