I was just wondering if someone could take a radiosity pic done in flamingo and
do a better one in Pov? Just like the lightwave thing that was done some time
ago. A friend of mine is all excited about Flamingo that he says does radiosity
faster and better than Pov. He hasn't bought Rhino &Flamingo yet but it looks
like he's going to. I just thought that maybe someone could help to give him a
more balanced view...

Regards.

--
/* Nekar Xenos */#local N=<-20,40,100>;#local K=<20,-40,100>;#local R=seed(0);
blob{#while((K-N).x>0)#local X=N;#local N=N+<rand(R),rand(R),1>/3;#local N=(
vlength(N-K)<vlength(X-K)?N:2*X-N);sphere{<N.y,-N.x,N.z>,1,1 scale .02}sphere{N
,1,1 scale.02}sphere{<-N.x-40,N.y,N.z>1,1 scale.01}sphere{<N.x+40,-N.y,N.z>1,1
scale.01 }#end pigment{rgbt 1}interior{media{emission <2,4,5>*5}}hollow}

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Nekar Xenos <j-p### [at] citywalkcoza> wrote:
: A friend of mine is all excited about Flamingo that he says does radiosity
: faster and better than Pov.

  The global lighting code of POV-Ray has still way to go, as it still has
some unknown problems (bugs?). AFAIK POV-Ray 3.5 will have basically the same
radiosity code as MegaPov has.
  In many scenes it works like a charm, very fast and the result is excellent.
However, it's quite usual that you just don't get it working in your
specific scene (either it's too dim or too bright or has annoying artifacts,
specially near corners; it also has this annoying tendency of working in
the way that if you set low quality you get good but unrealistic illumination
(eg. no darkening in corners) and if you set high quality you get better
illumination but annoying artifacts in corners). These problems might be
caused by wrong or buggy code. Perhaps a total rewrite could be necessary
in order to get rid of the problems (it seems that currently no-one knows
where the problems are in the radiosity code)?
  Anyways, the problem with POV-Ray radiosity is that it works in some
scenes but in others it has lots of problems. Other programs usually have
a working and bugless radiosity code and it usually works quite well in
all scenes.

  I'm not completely sure about this, but as far as I know, Radiance uses
a very similar montecarlo raytracing technique as POV-Ray uses in order
to calculate the radiosity, and the quality of Radiance images is quite
well known. Also, if I'm not completely wrong, the radiosity algorithm
of both programs are based on a paper of the same author (Greg Ward).
So the algorithm itself works well (as we can see from Radiance). It's just
the implementation in POV-Ray that has some problems.

-- 
#macro N(D,I)#if(I<6)cylinder{M()#local D[I]=div(D[I],104);M().5,2pigment{
rgb M()}}N(D,(D[I]>99?I:I+1))#end#end#macro M()<mod(D[I],13)-6,mod(div(D[I
],13),8)-3,10>#end blob{N(array[6]{11117333955,
7382340,3358,3900569407,970,4254934330},0)}//                     - Warp -

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"Nekar Xenos" <j-p### [at] citywalkcoza> wrote ;
>
> A friend of mine is all excited about Flamingo that he says does radiosity
> faster and better than Pov.

    Per dollar? Unless he is making money off his art, or has money to throw
away, POV is a -much- better value.

Post a reply to this message

> > A friend of mine is all excited about Flamingo that he says does
radiosity
> > faster and better than Pov.
>
>     Per dollar? Unless he is making money off his art, or has money to
throw
> away, POV is a -much- better value.

It depends on the value of your time, free software is only free if you know
how to use it or your time has no value.


--
Rick

Kitty5 WebDesign - http://Kitty5.com
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POV-Ray News & Resources - http://Povray.co.uk

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in news:3b1ccd95$1@news.povray.org Bill DeWitt wrote:

>> A friend of mine is all excited about Flamingo that he says does
>> radiosity faster and better than Pov. 
> 
>     Per dollar? Unless he is making money off his art, or has money
>     to throw 
> away, POV is a -much- better value.
> 

Per dollar?
Error ----> division by zero.

Ingo

-- 
Photography: http://members.home.nl/ingoogni/
Pov-Ray    : http://members.home.nl/seed7/

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"Warp" <war### [at] tagpovrayorg> wrote...
> So the algorithm itself works well (as we can see from Radiance). It's
just
> the implementation in POV-Ray that has some problems.

True.  It bugs me every time someone thinks that POV's algorithm is less
realistic because it is not "real" radiosity.  The goal is not "radiosity",
but rather "indirect illumination."  The radiosity algorithm is one way to
estimate indirect illumination, and monte carlo raytracing is simply another
method.  Both methods can produce either good or bad estimates, depending on
how much processor time you give them.

-Nathan

Post a reply to this message

Warp wrote:
> 
> Nekar Xenos <j-p### [at] citywalkcoza> wrote:
> : A friend of mine is all excited about Flamingo that he says does radiosity
> : faster and better than Pov.
> 
>   The global lighting code of POV-Ray has still way to go, as it still has
> some unknown problems (bugs?). AFAIK POV-Ray 3.5 will have basically the same
> radiosity code as MegaPov has.
>   In many scenes it works like a charm, very fast and the result is excellent.
> However, it's quite usual that you just don't get it working in your
> specific scene (either it's too dim or too bright or has annoying artifacts,
> specially near corners; it also has this annoying tendency of working in
> the way that if you set low quality you get good but unrealistic illumination
> (eg. no darkening in corners) and if you set high quality you get better
> illumination but annoying artifacts in corners). These problems might be
> caused by wrong or buggy code. Perhaps a total rewrite could be necessary
> in order to get rid of the problems (it seems that currently no-one knows
> where the problems are in the radiosity code)?

If you imagine radiosity as being like shading being applied to the
scene with a brush and diluted black ink, it becomes fairly easy to
understand.. well, for me anyway. (This analogy is kind of a butchery of
the way radiosity ACTUALLY works, but it's a fair description of its
effect on a scene.)

If you use a high error_bound, it's as if you were using a large brush,
or a sponge, to paint the shading on. This gives good overall lighting,
like a kind of "smart" ambient, but doesn't produce sharp shadows. It
also doesn't produce obvious artifacts, simply because the artifacts are
generally too large to be obvious. (Try lighting a "room" with
radiosity, using a high error_bound and a really low count. There should
be very noticible circles of varying brightness on the walls.)

If you use a low error_bound, the effect is that of using a small brush
to paint in the shadows with tiny strokes. Your lighting takes on a much
more noisy, grainy look - including artifacts in the corners, where
shadows "build up" - but shadow outlines are much more clearly defined.

For this analogy, imagine count as a measure of how thorough you are in
applying the ink with your brush. A low count represents strong ink,
applied quickly and sloppily. As you raise the count, you make more
strokes, using thinner ink, and the shadows take on more and more of a
"blended" look until finally they become smooth.

(The other parameters also have an effect on radiosity, of course, but
none of them are particularly important to this analogy. Many of them
are similar to count.)

Now, if you, a human being, were to attempt to shade a picture this way,
you would probably make an effort to put new splotches in the lighter
parts, so that even if the shading were grainy-looking, it would at
least be an even sort of graininess. But the computer makes no such
considerations, and when you imagine the result of randomly-placed
shading splotches, the reason for the artifacts becomes obvious...

Judging from old radiosity pics and the way official POV radiosity
works, I'd guess that whoever wrote the code never expected radiosity to
be used the way it's often used today. So it's not that the code is
buggy per se, it's just poorly-optimized for detail work, and what we
probably need is a smarter algorithm.

-Xplo

Post a reply to this message

"Xplo Eristotle" <xpl### [at] infomagiccom> wrote in message
news:3B1D8CC3.8DE0937E@infomagic.com...
> Warp wrote:
> >
> > Nekar Xenos <j-p### [at] citywalkcoza> wrote:
> > : A friend of mine is all excited about Flamingo that he says does radiosity
> > : faster and better than Pov.
> >
> >   The global lighting code of POV-Ray has still way to go, as it still has
> > some unknown problems (bugs?). AFAIK POV-Ray 3.5 will have basically the
same
> > radiosity code as MegaPov has.
> >   In many scenes it works like a charm, very fast and the result is
excellent.
> > However, it's quite usual that you just don't get it working in your
> > specific scene (either it's too dim or too bright or has annoying artifacts,
> > specially near corners; it also has this annoying tendency of working in
> > the way that if you set low quality you get good but unrealistic
illumination
> > (eg. no darkening in corners) and if you set high quality you get better
> > illumination but annoying artifacts in corners). These problems might be
> > caused by wrong or buggy code. Perhaps a total rewrite could be necessary
> > in order to get rid of the problems (it seems that currently no-one knows
> > where the problems are in the radiosity code)?
>
> If you imagine radiosity as being like shading being applied to the
> scene with a brush and diluted black ink, it becomes fairly easy to
> understand.. well, for me anyway. (This analogy is kind of a butchery of
> the way radiosity ACTUALLY works, but it's a fair description of its
> effect on a scene.)
>
> If you use a high error_bound, it's as if you were using a large brush,
> or a sponge, to paint the shading on. This gives good overall lighting,
> like a kind of "smart" ambient, but doesn't produce sharp shadows. It
> also doesn't produce obvious artifacts, simply because the artifacts are
> generally too large to be obvious. (Try lighting a "room" with
> radiosity, using a high error_bound and a really low count. There should
> be very noticible circles of varying brightness on the walls.)
>
> If you use a low error_bound, the effect is that of using a small brush
> to paint in the shadows with tiny strokes. Your lighting takes on a much
> more noisy, grainy look - including artifacts in the corners, where
> shadows "build up" - but shadow outlines are much more clearly defined.
>
> For this analogy, imagine count as a measure of how thorough you are in
> applying the ink with your brush. A low count represents strong ink,
> applied quickly and sloppily. As you raise the count, you make more
> strokes, using thinner ink, and the shadows take on more and more of a
> "blended" look until finally they become smooth.
>
> (The other parameters also have an effect on radiosity, of course, but
> none of them are particularly important to this analogy. Many of them
> are similar to count.)
>
> Now, if you, a human being, were to attempt to shade a picture this way,
> you would probably make an effort to put new splotches in the lighter
> parts, so that even if the shading were grainy-looking, it would at
> least be an even sort of graininess. But the computer makes no such
> considerations, and when you imagine the result of randomly-placed
> shading splotches, the reason for the artifacts becomes obvious...
>
> Judging from old radiosity pics and the way official POV radiosity
> works, I'd guess that whoever wrote the code never expected radiosity to
> be used the way it's often used today. So it's not that the code is
> buggy per se, it's just poorly-optimized for detail work, and what we
> probably need is a smarter algorithm.
>
> -Xplo

Thanks for this explanation. I've understood the basic principle of radiosity
without really knowing how to use it. This will really help me to use it better.

-Nekar

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"Rick [Kitty5]" <ric### [at] kitty5com> wrote in message
news:3b1ce9e9@news.povray.org...
>
> > > A friend of mine is all excited about Flamingo that he says does
> radiosity
> > > faster and better than Pov.
> >
> >     Per dollar? Unless he is making money off his art, or has money to
> throw
> > away, POV is a -much- better value.
>
> It depends on the value of your time, free software is only free if you
know
> how to use it or your time has no value.


    As I said, unless he is making money off his art. Hobby time has no
monetary value so you cannot include it in a dollar value calculation.

Post a reply to this message

"Bill DeWitt" <bde### [at] cflrrcom> wrote in message
news:3b1e1b15$1@news.povray.org...
>
>     As I said, unless he is making money off his art. Hobby time has no
> monetary value so you cannot include it in a dollar value calculation.
>

Bread-head.

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