POV-Ray : Newsgroups : povray.newusers : Creating soft shadows : Re: Creating soft shadows Server Time
17 Aug 2022 03:23:21 EDT (-0400)
  Re: Creating soft shadows  
From: Alain Martel
Date: 4 Dec 2021 10:18:44
Message: <61ab86d4$1@news.povray.org>
Le 2021-12-03 à 16:16, Kenneth a écrit :
> Alain Martel <kua### [at] videotronca> wrote:
>> For the two cylinders, adaptive 1, or maybe even adaptive 0, would
>> probably have been enough.
>> For the text object, it's not. You probably need to use adaptive 3 or
>> even 4 to get a correct result.
> You're correct with both suggestions. And for the letters, I cranked up adaptive
> to 5(!), which continued to make the letter shadows even smoother... but with a
> slower render, of course.
> But that's odd behavior, and does not agree with the documentation about
> 'adaptive': For my tests, I used a 'linear' light array of   1,33  which is
> 'only' 33 lights (1*31). According to the docs,
> "The number of rays never exceeds the values you specify for rows and columns of
> points."

It can't exceed the specified values in one direction. It's per 
direction, not total.
If the number of elements for the two directions are not the same, then, 
the initial sampling can be different.

> So for 33 lights in my area_light, the maximum *useful* adaptive value should be
>         adaptive 2  (5X5=25 rays)

In your case, that's 1x5 rays when using adaptive 2. The number of 
samples in the U direction is limited to 1, while the number of samples 
in the V direction can reach up to 33.

> But the adaptive mechanism is definitely still working at values of 3 through 5;
> I did some visual 'difference' tests to confirm this-- and the render times get
> slower as well.
> I am currently running POV-ray v3.8.0 beta 1 in Windows, so the way 'adaptive'
> works may have changed(?) at some point...or else there is something fundamental
> about the doc's description of 'adaptive' that I still don't understand.
In your scene, the actual starting sampling are :
adaptive 0 : 1x2
adaptive 1 : 1x3
adaptive 2 : 1x5
adaptive 3 : 1x9
adaptive 4 : 1x17
adaptive 5 : 1x33

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