POV-Ray : Newsgroups : povray.advanced-users : Speeding up media : Re: Speeding up media Server Time
6 Jul 2022 19:24:47 EDT (-0400)
  Re: Speeding up media  
From: Thomas de Groot
Date: 16 Feb 2021 02:36:33
Message: <602b7601$1@news.povray.org>
Op 15/02/2021 om 18:39 schreef Ash Holsenback:
> On 2/15/21 6:00 AM, William F Pokorny wrote:
>> On 2/15/21 2:37 AM, Thomas de Groot wrote:
>>> Op 14/02/2021 om 20:38 schreef Ash Holsenback:
>>>> On 2/14/21 2:33 PM, Ash Holsenback wrote:
>>>>> On 2/14/21 12:32 PM, Alain Martel wrote:
>>>>>> Le 2021-02-14 à 11:02, Ash Holsenback a écrit :
>> ...
>>> Give that man a beer!
>>>
>>> Much better assuredly.
>>>
>>> Pending more learned answers on your last question, I would be wary 
>>> to affirm this. The point being probably - if those are silently 
>>> ignored by method 3 as Alain states - that people will wring 
>>> themselves into hoops only to see some 'improvements' to their media, 
>>> without any results obviously. If, on the other hand, those are /not/ 
>>> ignored, we need to be dead sure about it. What does the code say, Mr 
>>> Pokorny?
>>>
>>
>> Generally, I recommend we make the recommendation to use only media 3 
>> more strongly. Using the other methods with the current code base is 
>> potentially confusing given they won't get some of the normal defaults 
>> due how the flip to method 3 was done in the parsing phase.
>>
>> I agree with Alain. The keywords: confidence, variance and ratio are 
>> used only with methods 1 and 2 (a). The use of the variance word in 
>> the method 3 wording is I suppose correct, but unfortunate. Another 
>> sample is taken between two existing, if the difference between the 
>> two end samples is > the aa_threshold.
>>
>> (a) For the purposes of documentation see (a1) and ignore the rest of 
>> this footnote. Someone can set the intervals in method 3 to more than 
>> 1 and if they do ratio does come into play with a lit and un-lit 
>> intervals scheme internally which 'probably' doesn't have much of an 
>> end effect for method 3, but... Always true, sometimes, almost never, 
>> never? Not sure... When using multiple medias with mixed sampling 
>> types, I know of some bleed through in the keyword settings between 
>> methods.
>>
>> (a1) It would be good to somewhere add a note along the lines of: When 
>> using multiple medias, it's strongly recommend all use the same 
>> sampling method. With the current code there is some keyword setting 
>> bleed between methods.
>>
>> Aside: The sentence about monte carlo.... only applies to methods 1 
>> and 2.
>>
>> Aside: FWIW. In povr I plan to at least make it appear methods 1 & 2 
>> and their keywords do not exist at all (and I'll pull jitter from 
>> media 3). Ideally, I'll replace the whole of the current 
>> implementation with a new media 3 like one. There are standing issue 
>> with media 3 too with respect to speed, accuracy of result and when 
>> and if adaptive sampling actually kicks in. But, it's media - which is 
>> fuzzy. Most remaining issues don't matter much to an end result as I 
>> recall - so long as we sample enough that things look good. ;-)
>>
>> Bill P.
>>
>>
> 
> thanks /everyone/ for guidance and support... please review
> http://wiki.povray.org/content/Reference:Sampling_Parameters_%26_Methods

Yes. Add that note (a1) from Bill. That is important indeed. One trivial 
thing I want to suggest: Add an empty line between Methods. It would 
increase the readability even more.

[Maybe Alain will not have to repeat indefinitely anymore about method 
3, intervals 1, and single samples.... ;-) ]

-- 
Thomas


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