I have made some tests with variable radiosity parameters.  See 

news://news.povray.org/3d6f88fa%40news.povray.org

for the discussion on this subject.

Varying count seems much more useful than varying error_bound.  It's also
possible that changing error_bound depending on the position has some side
effects that are problematic.  In any case the overhead produced by a
function based count value is much lower since the function only has to be
evaluated for every radiosity sample taken while an error_bound function
has to be called for every Compute_Ambient() call.

The following pictures show a fairly simple example.  The first is
rendered with a fixed count of 60, the second with varying count.  The
last shows the simple function used for defining the count: red means low
count (<20), yellow 20-50, blue >50. 

The render times were:
 126 seconds for fixed count 
 138 seconds for variable

about 13000 radiosity samples (and function VM calls), error_bound was
0.4, pretrace_start 1, pretrace_end 1/image_width, recursion_limit 2.

I think the difference is noticeable, notice especially the artefacts on
the outside of the cubicle.  Anyway the parts with low count are looking
noticably worse too and the render time is longer.  Testing with a real
scene and a better optimized function for the count value would be
important of course.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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Attachments:
Download 'var_rad_1.png' (70 KB) Download 'var_rad_2.png' (74 KB) Download 'var_rad_fn.png' (77 KB)

Preview of image 'var_rad_1.png'

Preview of image 'var_rad_2.png'

Preview of image 'var_rad_fn.png'

Christoph Hormann wrote:
> 
> I have made some tests with variable radiosity parameters.
> 
> [...]

No comments concerning this?

At least some 'looks useful' of 'i could not think of anything this would
be needed for' would be nice.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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Okay, okay, a comment. The variable version
does look better, but how difficult is it to set?

I mean, if you simply have to add "use_variable_count on",
that's nice, but if you'd got to build a function
describing the basic layout of the scene...

Don't know.


--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

>
> No comments concerning this?
>
> At least some 'looks useful' of 'i could not think of anything this would
> be needed for' would be nice.
>

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On Tue, 03 Sep 2002 15:40:24 +0200, Christoph Hormann <chr### [at] gmxde>
wrote:
> No comments concerning this?

I'm an amoteur in radiosity so not started anything, sorry

> At least some 'looks useful' of 'i could not think of anything this would
> be needed for' would be nice.

Nice colors. :-)

ABX

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Christoph Hormann wrote: 
> Christoph Hormann wrote:
>> 
>> I have made some tests with variable radiosity parameters.
>> 
>> [...]
> 
> No comments concerning this?

OK: Some day I should also start to care about radiosity parameters --
at least to the extent that I understand your post. ;-)

Thomas

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Tim Nikias wrote:
> 
> Okay, okay, a comment. The variable version
> does look better, but how difficult is it to set?
> 
> I mean, if you simply have to add "use_variable_count on",
> that's nice, but if you'd got to build a function
> describing the basic layout of the scene...
> 

Well, if you have a suggestion how to define the count that is easier to
set up i would be pleased to hear.  As already explained defining it on
per object basis would not be very useful.

And it's not that difficult with functions after all, you can for example
use a df3 file to describe what parts of the scene you need high count
for.

Another idea i have been thinking about is adaptive count.  This would
mean when taking a sample the program shoots a minimum number of rays,
analyzes their results and decides whether to shoot more.  

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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ABX wrote:
> 
> [...]
> 
> Nice colors. :-)
> 

:-)

I already feared to get replies like that now, but considering radiosity
was quite commonly used recently i assumed there would be more interest in
such extensions.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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Christoph Hormann wrote:
> And it's not that difficult with functions after all, you can for example
> use a df3 file to describe what parts of the scene you need high count
> for.

  That's inseresting...
 
> Another idea i have been thinking about is adaptive count.  This would
> mean when taking a sample the program shoots a minimum number of rays,
> analyzes their results and decides whether to shoot more.

  ...but that would be ideal for lazy raytracers like me. I always prefer 
these things to be automatic (because if they depend on my knowledge of 
inner working, I'm lost).

-- 
Jaime Vives Piqueres

La Persistencia de la Ignorancia
http://www.ignorancia.org

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3D74CA7E.E59ED0AA@gmx.de...

> I already feared to get replies like that now, but considering radiosity
> was quite commonly used recently i assumed there would be more interest in
> such extensions.

I guess that the lack of answers is due to the fact that demo doesn't show
off the benefit of it as some artefacts disappear but other come up (like
the brighter spots in the middle of the walls or on the underside of the
door). And the render time is longer too, which is an undesired effect I
suppose.

Still any idea about controlling the radiosity quality is interesting and
may prove to be valuable, so keep on trying !!! And like Jaime says, the
more automatic the better...

G.


--

**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters

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Jaime Vives Piqueres wrote:
> 
> > Another idea i have been thinking about is adaptive count.  This would
> > mean when taking a sample the program shoots a minimum number of rays,
> > analyzes their results and decides whether to shoot more.
> 
>   ...but that would be ideal for lazy raytracers like me. I always prefer
> these things to be automatic (because if they depend on my knowledge of
> inner working, I'm lost).

But it would not have the same effect.  With the demonstrated technique i
intended to give the user a tool to do something about specific artefacts
by locally increasing the count value.  The adaptive method would (if it
works, i have not tried yet) increase quality in general while not
increasing render time too much.  Without doubt this would be useful, but
it would not be a replacement for the other technique.

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 13 Aug. 2002 _____./\/^>_*_<^\/\.______

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