POV-Ray : Newsgroups : povray.beta-test.binaries : Radiosity POV 3.6 vs. 3.7 vs. MCPov : Re: Radiosity POV 3.6 vs. 3.7 vs. MCPov Server Time
23 Feb 2024 22:49:15 EST (-0500)
  Re: Radiosity POV 3.6 vs. 3.7 vs. MCPov  
From: clipka
Date: 18 Jan 2009 21:30:01
Message: <web.4973e4ca516c009ab2c85f720@news.povray.org>
Ive <"ive### [at] lilysoftorg"> wrote:
> I have no explanation why the reflection in the mirror looks different
> in the MCPov version. And in fact it makes me quite unhappy, it looks
> somewhat desaturated.

Hum... maybe max trace level issues of sorts...?

> > - The 3.6.1 shot looks rather dark; I attribute this to the windows and flaws in
> > POV 3.6 radiosity: When gathering deep-recursion samples, POV 3.6 effectively
> > just traced a single level, so I guess it will not make it through the windows.
> > All 3rd-bounce samples will probably be pitch black, and possibly even the
> > 2nd-bounce ones.
> >
>
> In fact there is NO window "glass", there is just empty space ;)

Hum again... okay, so there is no spoon...

If the scene is just radiosity-lit, and materials are defined deliberately to be
identical, then the only thing I can think of that could cause a significant
bias to any particular color (like, for example, black) is POV-Ray giving up on
some rays due to max trace level, ADC bailout or similar (i.e. recursion depth
in case of radiosity) - in which cases POV will invariably use pitch black as
substitute.

So the way a version of POV "counts" recursion depth might make a difference
regarding how much black is mixed in.

Does a significant portion of surfaces in your shot have reflective components?


> > - The 3.7 shot indeed looks weird - but this weirdness look distinctively
> > familiar: "Ambient" immediately comes to mind.
>
> Nope. All materials do use ambient 0 in the finish statement and no
> default include files are used where something else might be specified.

That's perfectly weird. In all tests shots, I have never seen such effects. Note
that the white tiles do not only "bleed" onto the walls - they themselves look
overly bright.

Something gets a >1 term into it somewhere.

Again: Does a significant portion of surfaces in your shot have reflective
components?

Assuming for now that the tiles are partially reflective - is the sum of their
"reflection" and "diffuse" values possibly >1?

Note that this breaks the law of conservation of energy. This is not an issue in
classically-lit POV scenes, because of the strict separation between "images"
and "light sources"; however, in radiosity scenes it can become dramatic.

I can imagine that MCPov *might* handle such situations automatically as a side
effect of its design. However, I'm quite sure standard POV does not.


Just to make sure: We are talking about 3.7.0.beta.30-rad1, right?


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