POV-Ray : Newsgroups : povray.documentation.inbuilt : Corrections to documented media defaults. : Re: Corrections to documented media defaults. Server Time
24 Jun 2021 07:30:11 EDT (-0400)
  Re: Corrections to documented media defaults.  
From: William F Pokorny
Date: 16 Feb 2018 08:24:51
Message: <5a86dba3$1@news.povray.org>
On 02/15/2018 11:11 PM, Kenneth wrote:
> William F Pokorny <ano### [at] anonymousorg> wrote:
...
> 
> What's also missing from all of the various media wiki references I've looked at
> is that, with method 3, a *single* samples value can be used instead...
> 
> samples  35
> 
> ....but even then, it isn't clear if method 3 is the *only* method that can do
> that. Do methods 1 and 2 *require* 2 values?
> 
> The docs do need updating about this-- but I'm wondering if, sometime within the
> v3.5-to-3.7 interval, the default samples value changed more than once(?) In
> which case, changing the docs' default to  samples 10 (or 10,10?)  might raise
> questions for users of those older versions-- if samples 1,1  as the default
> 'came and went' with various versions.  (Of course, that predicament cold be
> easily solved with an extra note in the docs, about old vs. new behavior.)
> 

Agree further doc updates are needed. As I dig deeper into media I'm 
gathering a list of other documentation updates that would be helpful I 
think including some of what you discuss. Trying not to go after too 
much at once - and some behavior suppose we might change sooner rather 
than later.

For example, while I've never made use of photons beyond playing with 
the distribution sample scenes, I now know it's "method" for media is 
it's own thing. 'Method photons' - suppose I see it as most like method 
2 at this point - is not using at all the sample or jitter settings for 
example. ...and I think photon jitter put into the photon media 
depositing while debugging and got left in accidentally. I can see no 
reason to introduce the banding artifact - see our optics.pov scene 
(more visible if you reduce the media gather radius but it's there in 
the scene we ship). The default jitter should be the full 1.0 always as 
far as I can see.

We have this page:

http://wiki.povray.org/content/Reference:Sampling_Parameters_%26_Methods#Index_Entry_method_media

where it might be good to mention the effective method 'photons', how it 
is different, how it can and cannot be controlled by media block 
settings.  There is limited documentation where the photons feature is 
documented.

(Yes, that page lists the default method 3 aa_level as 4 when it's 3 as 
indicated on the initial wiki page of this thread.)

Anyway... Also so much of the whole of media behavior I still don't 
understand.

Bill P.


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