Can anybody explain to me how the sampling parameters for media actually 
work? This is one of the few areas where POV-Ray's documentation seems a 
little unclear. (In particular, apparently there are 3 sampling 
methods... but I'm really fuzzy on how they work.)

In particular, the documentation says that the default setting for 
invertals is 10. However, when I put that into my scene, the render 
slows down *drastically*. (And the image quality improves.) What's going on?

Also, do the sampling parameters still have an effect when you're using 
media photons? Do the photon sampling parameters override that? Do the 
media parameters control how much POV-Ray samples the photon map it's 
already built? How does this part work??

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Orchid XP v3 <voi### [at] devnull> wrote:
> In particular, the documentation says that the default setting for 
> invertals is 10.

  The documentation is old in this regard. It lists the defaults for
method 1, but the default method is 3, which has different defaults.
  AFAIK this will be fixed in 3.7.

-- 
                                                          - Warp

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>> In particular, the documentation says that the default setting for 
>> invertals is 10.
> 
>   The documentation is old in this regard. It lists the defaults for
> method 1, but the default method is 3, which has different defaults.
>   AFAIK this will be fixed in 3.7.

Ah, I see...

So do you happen to know what the *real* defaults are? (Obviously 
method=3, so I'm presuming intervals=1 and samples=??)

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Orchid XP v3 <voi### [at] devnull> wrote:
> >> In particular, the documentation says that the default setting for
> >> invertals is 10.
> >
> >   The documentation is old in this regard. It lists the defaults for
> > method 1, but the default method is 3, which has different defaults.
> >   AFAIK this will be fixed in 3.7.
>
> Ah, I see...
>
> So do you happen to know what the *real* defaults are? (Obviously
> method=3, so I'm presuming intervals=1 and samples=??)

From a brief look at the source for 3.6, the defaults listed in the
documentation are correct for versions earlier than 3.5 (except perhaps
that the default aa_level appears to be 3, not 4). This includes a media
method of 1 (hence the default intervals of 10).

Some of these values are then altered immediately during parsing for
versions 3.5 and later. It looks like the properties that change are:

method 3
intervals 1
samples 10,10

It's easily possible that these or other parameters change later on in the
code, I haven't looked very thoroughly, but I don't think they can be
serious differences based on simple test renders.

Tom

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Orchid XP v3 nous apporta ses lumieres en ce 08/10/2006 07:36:
> Can anybody explain to me how the sampling parameters for media actually 
> work? This is one of the few areas where POV-Ray's documentation seems a 
> little unclear. (In particular, apparently there are 3 sampling 
> methods... but I'm really fuzzy on how they work.)
> 
> In particular, the documentation says that the default setting for 
> invertals is 10. However, when I put that into my scene, the render 
> slows down *drastically*. (And the image quality improves.) What's going 
> on?
> 
> Also, do the sampling parameters still have an effect when you're using 
> media photons? Do the photon sampling parameters override that? Do the 
> media parameters control how much POV-Ray samples the photon map it's 
> already built? How does this part work??
method 3
intervals 1

Instead of increasing intervals, increase samples.
intervals 10 samples 10 give you 100 samples
intervals 1 samples 100 does the same BUT is much faster. samples 300 is still 
faster than intervals 10 samples 10.

The sampling parameter DOES affect photons sampling in media. It works 
complementary with the photons parameters.

-- 
Alain
-------------------------------------------------
To the world you may be one person, but to one person you may be the world.

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"Tom York" <alp### [at] zubenelgenubi34spcom> wrote:

> Some of these values are then altered immediately during parsing for
> versions 3.5 and later. It looks like the properties that change are:
>
> method 3
> intervals 1
> samples 10,10

I came to the same conclusions, from doing a series of purely visual tests
awhile back. I believe Warp also posted a similar conclusion in an older
thread. (Sorry, can't remember when or where.)

Ken W.

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