POV-Ray : Newsgroups : povray.documentation.inbuilt : Anti-aliasing mode 3 : Re: Anti-aliasing mode 3 Server Time
28 Nov 2021 09:12:31 EST (-0500)
  Re: Anti-aliasing mode 3  
From: clipka
Date: 23 Sep 2018 08:25:15
Message: <5ba7862b$1@news.povray.org>
Am 23.09.2018 um 13:49 schrieb Jim Holsenback:
> On 9/23/18 7:36 AM, Jim Holsenback wrote:
>>> ----------------------------------------------------------
>>> Another way to reduce anti-aliasing artifacts is to introduce noise into
>>> the sampling process. This is called jittering and works because the
>>> human visual system is much more forgiving to noise than it is to
>>> regular patterns, and is inherent in anti-aliasing mode 3. When using
>>> one of the other methods, the location of the super-samples is also
>>> jittered or wiggled a tiny amount jittering by default, but may be
>>> turned off with the Jitter=off option or -J option, or the amount of
>>> jittering can be set with the Jitter_Amount=n.n option. When using
>>> switches the jitter scale may be specified after the +Jn.n option. For
>>> example +J0.5 uses half the normal jitter. The default amount of 1.0 is
>>> the maximum jitter which will insure that all super-samples remain
>>> inside the original pixel.
>>> -----------------------------------------------------------
> 
> one more thing i just thought of...so is -j is useless if using +am3.
> does it throw a warning if the user specifies? i couldn't check because
> i'm in the middle of my variation of RSOCP...GSOPP (glowing spheres on
> pavement plane) beauty run

`+j/-j` has no effect whatsoever when using `+am3`.

I'm not sure whether throwing a warning would be the right thing to do;
it's not general policy to throw warnings for using INI file or
command-line settings that turn out to be without effect due to the
other settings. For example, `+am3` by itself (without `+a`) has no
effect either and also doesn't give you a warning.

This actually makes sense, if you consider that you can set up INI stuff
in the master povray.ini. For example, a user might deliberately specify

    Antialias=off
    Sampling_Method=3
    Antialias_Confidence=0.95
    Antialias_Threshold=0.02
    Jitter=off
    Jitter_Amount=0.2

in their povray.ini to tell POV-Ray that they normally want no
anti-aliasing, but if they do they prefer method 3 with a confidence of
95% and a threshold of 2%, and if they choose a different method they
want no jitter, and if they explicitly turn on jitter they want just a
little of it.

Such a user wouldn't want a warning every time they start a render.


The portions of POV-Ray concerned with the /semantics/ of the ini and
command-line settings cannot tell whether they came from a povray.ini, a
quickres.ini, a scene-specific ini or the command-line, whether they
were specified using ini file style or command-line style, nor even the
order in which they were issued, so they are unable to tell whether the
specific settings were intentional as in the above example, or by
mistake as might be presumed in a `+am3 -j` command-line.


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