Hi all,

In an attempt to get a clean render, I am trying to tune
the radiosity settings for the scene.

With the following settings I get round splotches as shown
on the attached image. I tried various changes in the settings
making the splotches smaller, or changing their location,
but to date, I still have round splotches. (I manage to find these
by comparing with other settings renders ; with nearest_count 10
splotches move and are less visible, yet there are still splotches).

Has anyone of you encountered such splotches and managed to
get rid of them ? Any suggestion ?

Here are the settings :

global_settings {
  charset utf8
  adc_bailout 0.001
  max_trace_level 10
  #if(Rad)
    radiosity{
      pretrace_start 0.04
      pretrace_end   0.02
      count 300
      nearest_count 5
      error_bound 0.07
      recursion_limit 1
      low_error_factor .5
      minimum_reuse 0.01
      brightness 1
      adc_bailout 0.01
    }
  #end
}

Vincent

P.S. Splotches are apparently linked to reflection finish
(finish { reflection { 0.0, 0.5 } }) of the dragons. The same
scene with matte dragons has no splotches...

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Attachments:
Download 'sphere_dragon__bigger_sphere_04_05bc__1h26_splotches.png' (447 KB)

Preview of image 'sphere_dragon__bigger_sphere_04_05bc__1h26_splotches.png'

Vincent L. escreveu:
> With the following settings I get round splotches as shown
> on the attached image. I tried various changes in the settings
> making the splotches smaller, or changing their location,
> but to date, I still have round splotches. (I manage to find these
> by comparing with other settings renders ; with nearest_count 10
> splotches move and are less visible, yet there are still splotches).
> 
> Has anyone of you encountered such splotches and managed to
> get rid of them ? Any suggestion ?

Even the best get some radiosity splotches in pov-ray, like Gilles 
Tran's awarded wikipedia glasses image:

http://en.wikipedia.org/wiki/Image:Glasses_800_edit.png

There's one single splotch near the bottom.  Impressive, given all the 
glasses and reflections!

sources here:
http://www.oyonale.com/modeles.php?lang=en&page=40

He uses a simple
global_settings {
     assumed_gamma 1
     max_trace_level 30
     #if (RadOK>0)
         radiosity {
             #if (RadOK=1)
                 count 50
                 error_bound 2
             #else
                 count 200
                 error_bound 0.1
             #end
             recursion_limit 2
             nearest_count 8
             brightness 1
             normal on
         }
     #end
}

and RadOK = 2 for max quality...

> P.S. Splotches are apparently linked to reflection finish
> (finish { reflection { 0.0, 0.5 } }) of the dragons. The same
> scene with matte dragons has no splotches...

Yes.  But I'd say the only splotch I'm able to spot in your scene is the 
one in the ground.  Other than that, the ground lines look terribly 
jaggy or something...

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"Vincent L." <nomail@nomail> wrote:
> Hi all,
>
> With the following settings I get round splotches as shown
> on the attached image. [...]
>

Frankly I can to see them.

But the image is very attractive!

Post a reply to this message

"Vincent L." <nomail@nomail> wrote:
> Hi all,
>
> In an attempt to get a clean render, I am trying to tune
> the radiosity settings for the scene.
>
> With the following settings I get round splotches as shown
> on the attached image. I tried various changes in the settings
> making the splotches smaller, or changing their location,
> but to date, I still have round splotches. (I manage to find these
> by comparing with other settings renders ; with nearest_count 10
> splotches move and are less visible, yet there are still splotches).
>
> Has anyone of you encountered such splotches and managed to
> get rid of them ? Any suggestion ?
>
> Here are the settings :
>
> global_settings {
>   charset utf8
>   adc_bailout 0.001
>   max_trace_level 10
>   #if(Rad)
>     radiosity{
>       pretrace_start 0.04
>       pretrace_end   0.02
>       count 300
>       nearest_count 5
>       error_bound 0.07
>       recursion_limit 1
>       low_error_factor .5
>       minimum_reuse 0.01
>       brightness 1
>       adc_bailout 0.01
>     }
>   #end
> }
>
> Vincent
>
> P.S. Splotches are apparently linked to reflection finish
> (finish { reflection { 0.0, 0.5 } }) of the dragons. The same
> scene with matte dragons has no splotches...


The splotches are sampling errors and can be fixed.
Offhand, why is your nearest_count so low? And your pretrace_end could be
smaller, which can allow you to reduce artifacts with such a small error_bound
(without boosting the count).

I am not sure of what you prefer, appearance-wise, but I would change your
radiosity block to:

radiosity{
    pretrace_start 0.080
    pretrace_end   0.005
    count 200
    nearest_count 20
    error_bound 0.07
    recursion_limit 3
    low_error_factor .5
    minimum_reuse 0.01
    brightness 1
    adc_bailout 0.01
}


This is just a guess, though, as radiosity needs to be tuned to fit the user's
quality/speed preferences.

  If possible, can you read through and try what is recommended in the radiosity
tuning guide in the wiki?  The techniques in it have worked well for me and I am
always looking to improve the article.  I still quite a few radiosity questions
on the newsgroups that I thought may have been covered by it, but no one
mentions it, so I don't know if people read it and it didn't work for them, or
if people are just not aware of it.

Another thought is that if it is only associated with reflection, you could use
load_file and save_file to sidestep this.



    -Reactor

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"Reactor" <rea### [at] hotmailcom> wrote:

>   If possible, can you read through and try what is recommended in the radiosity
> tuning guide in the wiki?  The techniques in it have worked well for me and I am
> always looking to improve the article.  I still quite a few radiosity questions
> on the newsgroups that I thought may have been covered by it, but no one
> mentions it, so I don't know if people read it and it didn't work for them, or
> if people are just not aware of it.

I'm probably one of those folks; I continue to forget that there *is* a wiki. At
present, there's no link to it on the newsgroups page--where I usually go--just
on the povray.org page. Hopefully that will change in future...for myopic
people like me.  :-)

Ken W.

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> In an attempt to get a clean render, I am trying to tune
> the radiosity settings for the scene.

You could try MCPov if you are willing to wait for a bit longer render (but 
with much less set up time).  I have found MCPov gives superb results where 
radiosity was just getting too tricky (or impossible) to tune for the scene.

Post a reply to this message

scott wrote:

> You could try MCPov if you are willing to wait for a bit longer render
> (but with much less set up time).  I have found MCPov gives superb
> results where radiosity was just getting too tricky (or impossible) to
> tune for the scene.

It would be nice to see a reference render with MCPov. That way you can
at least know what it should look like...

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scott napsal(a):
>> In an attempt to get a clean render, I am trying to tune
>> the radiosity settings for the scene.
> 
> You could try MCPov if you are willing to wait for a bit longer render 
> (but with much less set up time).  I have found MCPov gives superb 
> results where radiosity was just getting too tricky (or impossible) to 
> tune for the scene.
> 
> 
actually I like the noise because it makes the image look more like a 
photo and because shot noise actually happens in the reality (though not 
as much).

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>> You could try MCPov if you are willing to wait for a bit longer render
>> (but with much less set up time).  I have found MCPov gives superb
>> results where radiosity was just getting too tricky (or impossible) to
>> tune for the scene.
>
> It would be nice to see a reference render with MCPov. That way you can
> at least know what it should look like...

Yep agreed, btw here is one of my renders with MCPov. I was having trouble 
with splotches appearing inside the shelf (particularly along the back edge, 
where I guess POV was shooting a radiosity sample "through" the back wall). 
I tried all sorts of things as well as the actual radiosity settings, like 
making the walls thicker, changing the geometry around the back, but still 
there were splotches.  In the end it was quicker (and less work for me!) to 
just set MCPov off on it overnight and come back to a perfect render!

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Attachments:
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