POV-Ray : Newsgroups : povray.general : media ignores an EVEN number of samples Server Time: 22 Oct 2017 21:03:28 GMT
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From: Kenneth
Subject: Re: media ignores an EVEN number of samples
Date: 21 May 2017 21:55:01
Message: <web.59220c411d3e9755883fb31c0@news.povray.org>
clipka <ano### [at] anonymousorg> wrote:
> Am 21.05.2017 um 18:28 schrieb Kenneth:
> >
> > Regarding intervals, are those *partial* shadows in the category of
> > 'illuminated intervals' or not? It's a mystery to me!
>
> I've never really looked at the intervals mechanism in detail (I just
> know that they exist), but I can't imagine it being able to detect such
> cases. I wouldn't even know how it could possibly detect the shadows of
> objects. Such effects can only be detected on a sub-interval basis.
>
> So from what I know, the intervals mechanism can only identify the
> boundaries of spotlights, and/or possibly overlapping media containers
> (though I guess the latter is handled at a higher level).

Well, it heartens me to know that bigger brains than mine are having a bit of
trouble with this too ;-)

I've been re-reading the docs about this stuff (again!), and see another
sentence in 'ratio' that may--or may not?-- need clarifying: "The ratio keyword
distributes intervals differently between lit and unlit areas." I think it
should say SAMPLES rather than 'intervals', because the following sentence then
makes more sense: "The default value of ratio 0.9 means that lit intervals get
more samples than unlit intervals." Are INTERVALS actually "distributed
differently" too??

That little paragraph about 'ratio' has given me WAY too much trouble in the
past; it's now my sworn duty to try and improve it ;-)


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From: Alain
Subject: Re: media ignores an EVEN number of samples
Date: 23 May 2017 00:29:27
Message: <59238267$1@news.povray.org>
Le 17-05-21 à 17:53, Kenneth a écrit :
> clipka <ano### [at] anonymousorg> wrote:
>> Am 21.05.2017 um 18:28 schrieb Kenneth:
>>>
>>> Regarding intervals, are those *partial* shadows in the category of
>>> 'illuminated intervals' or not? It's a mystery to me!
>>
>> I've never really looked at the intervals mechanism in detail (I just
>> know that they exist), but I can't imagine it being able to detect such
>> cases. I wouldn't even know how it could possibly detect the shadows of
>> objects. Such effects can only be detected on a sub-interval basis.
>>
>> So from what I know, the intervals mechanism can only identify the
>> boundaries of spotlights, and/or possibly overlapping media containers
>> (though I guess the latter is handled at a higher level).
> 
> Well, it heartens me to know that bigger brains than mine are having a bit of
> trouble with this too ;-)
> 
> I've been re-reading the docs about this stuff (again!), and see another
> sentence in 'ratio' that may--or may not?-- need clarifying: "The ratio keyword
> distributes intervals differently between lit and unlit areas." I think it
> should say SAMPLES rather than 'intervals', because the following sentence then
> makes more sense: "The default value of ratio 0.9 means that lit intervals get
> more samples than unlit intervals." Are INTERVALS actually "distributed
> differently" too??
> 
> That little paragraph about 'ratio' has given me WAY too much trouble in the
> past; it's now my sworn duty to try and improve it ;-)
> 
> 
> 
> 

When using sampling method 3, the default, ratio have no meaning.
You only need to think about total samples count. ratio, confidence and 
variance are not used. intervals need to stay at it's default value of 1.
Leave them out unless you use method 1 or 2 and save yourself from 
headaches.



Alain


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