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From: stm31415
Subject: Radiosity: is this appropriate?
Date: 11 Dec 2004 14:05:00
Message: <web.41bb441e2c73d0f48f722dab0@news.povray.org>
After a couple of IRTC submissions that used radiosity, and then getting
comments suggesting I should try using radiosity, I mean to get it right
this time. I have been using two-pass radiosity. I will post the image on
P.B.I.
Here is my problem. If I use a lower-quality first pass (count 500
error_bound .4 at 100*60) My lighting is just as flat on the second pass as
it always was. So now I am trying to use a 500*300 with the following
settings:


  radiosity {
        #if (pass1)
         pretrace_start .04
          pretrace_end   .01
         error_bound .1
         minimum_reuse .0025
         nearest_count 20
         count 1200
         recursion_limit 5
         brightness 1
         max_sample 2
         low_error_factor 1
         adc_bailout 0.01/20
         save_file "radios"
        #else

     pretrace_start 1
      pretrace_end   1
      count 1200
      recursion_limit 5
      low_error_factor .5
      gray_threshold 0.0
      brightness 1.25
      error_bound .8
      minimum_reuse .0025
      nearest_count 20
      low_error_factor 1
      adc_bailout 0.01/20
      load_file "radios"
      always_sample off
      max_sample 1
     #end
  }

but this, even with the simplified first pass scene, will take over 11 days
to render! By the time I get the second pass done, I'll have run out of
time. Have I forgotten something, or does a good render just take this
long? It seems like I have seen high quality images that did not take quite
so long.

Also, I am having trouble with the smoothed second pass. It seems to lose a
lot of detail in small areas (see the ceiling in the posted image)

I have read the docs several times though, as well as Tim Nikias' two-pass
radiosity experiments, but I'm still not quite getting that clean, crisp,
complex shadowed look.

Thank you for any advice you can give.

-S
5TF!


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From: Mike Thorn
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 14:08:46
Message: <41bb45be$1@news.povray.org>
I'm not an expert but I would lower your count by a lot. I saw no 
visible difference in my POVCOMP entry when I lowered it from 1200 to 
about 50, but it cut my time exponentially.

~Mike

stm31415 wrote:
> After a couple of IRTC submissions that used radiosity, and then getting
> comments suggesting I should try using radiosity, I mean to get it right
> this time. I have been using two-pass radiosity. I will post the image on
> P.B.I.
> Here is my problem. If I use a lower-quality first pass (count 500
> error_bound .4 at 100*60) My lighting is just as flat on the second pass as
> it always was. So now I am trying to use a 500*300 with the following
> settings:
> 
> 
>   radiosity {
>         #if (pass1)
>          pretrace_start .04
>           pretrace_end   .01
>          error_bound .1
>          minimum_reuse .0025
>          nearest_count 20
>          count 1200
>          recursion_limit 5
>          brightness 1
>          max_sample 2
>          low_error_factor 1
>          adc_bailout 0.01/20
>          save_file "radios"
>         #else
> 
>      pretrace_start 1
>       pretrace_end   1
>       count 1200
>       recursion_limit 5
>       low_error_factor .5
>       gray_threshold 0.0
>       brightness 1.25
>       error_bound .8
>       minimum_reuse .0025
>       nearest_count 20
>       low_error_factor 1
>       adc_bailout 0.01/20
>       load_file "radios"
>       always_sample off
>       max_sample 1
>      #end
>   }
> 
> but this, even with the simplified first pass scene, will take over 11 days
> to render! By the time I get the second pass done, I'll have run out of
> time. Have I forgotten something, or does a good render just take this
> long? It seems like I have seen high quality images that did not take quite
> so long.
> 
> Also, I am having trouble with the smoothed second pass. It seems to lose a
> lot of detail in small areas (see the ceiling in the posted image)
> 
> I have read the docs several times though, as well as Tim Nikias' two-pass
> radiosity experiments, but I'm still not quite getting that clean, crisp,
> complex shadowed look.
> 
> Thank you for any advice you can give.
> 
> -S
> 5TF!
> 
>


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From: stm31415
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 14:20:00
Message: <web.41bb4790420c6eda8f722dab0@news.povray.org>
There is DEFINITELY a difference in my image. At 50, 100, all the way up to
about 600 it has flat shadows, artefacting in the corners, and all over
boring lighting. I need my count to be at least 750 to look OK.

-S
5TF!


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From: Marc Jacquier
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 17:18:27
Message: <41bb7233$1@news.povray.org>

news:web.41bb4790420c6eda8f722dab0@news.povray.org...
> There is DEFINITELY a difference in my image. At 50, 100, all the way up
to
> about 600 it has flat shadows, artefacting in the corners, and all over
> boring lighting. I need my count to be at least 750 to look OK.
>
> -S
> 5TF!
>
how are set your finish{ambient}s?
if ambients are more than 0, you get luminous and flat shadows
set ambients to 0 unless you want texture to emit light (sky or light object
for instance)
if no ambient value is specified, default is 0.1
you can put #default {finish{ambient 0}} in global_settings block to set
your own default value

Marc


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From: stm31415
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 17:30:01
Message: <web.41bb746d420c6eda3947da9a0@news.povray.org>
Yeah, I had trouble with that previously, but the default ambient IS zero in
this image. Only the lights upstairs, and the sky are higher ambient. BTW,
it has speeded up a little, so it will now only take 8 days for a 500*300
render :(

-S
5TF!


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From: Christoph Hormann
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 18:15:02
Message: <cpfuog$2kk$1@chho.imagico.de>
stm31415 wrote:
> After a couple of IRTC submissions that used radiosity, and then getting
> comments suggesting I should try using radiosity, I mean to get it right
> this time. I have been using two-pass radiosity. I will post the image on
> P.B.I.
> Here is my problem. If I use a lower-quality first pass (count 500
> error_bound .4 at 100*60) My lighting is just as flat on the second pass as
> it always was. So now I am trying to use a 500*300 with the following
> settings:
> 
> 
> [...]

Those settings don't appear very useful - start with the default or with 
one of the settings from rad_def.inc and only modify something when you 
know it has the intended effect.  Simply randomly trying out numbers 
won't lead you anywhere except to long render times.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 23 Sep. 2004 _____./\/^>_*_<^\/\.______


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From: stm31415
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 19:55:00
Message: <web.41bb95d4420c6eda607ddbe00@news.povray.org>
>
> Those settings don't appear very useful - start with the default or with
> one of the settings from rad_def.inc and only modify something when you
> know it has the intended effect.  Simply randomly trying out numbers
> won't lead you anywhere except to long render times.
>
> Christoph
>
> --

Well, let me explain why I used them, and hopefully someone can tell me
where I went wrong.

 radiosity {
        #if (pass1)
         pretrace_start .04    <--- The pretraces, I reduced in size to get
a little more variation in the colors and shadows of that big, blank far
wall, by avoinding large sample areas.
          pretrace_end   .01   <--- See above
         error_bound .1 <-- I reduced the error bound until it looked good.
Larger is too low quality, and lower changes very little.
         minimum_reuse .0025 <--  The default.
         nearest_count 20 <--I was using this because that's what Tim Nikias
reccomended for 2 pass radiosity. Ensures more even samples, as I
understand it.
         count 1200 <-- I used a high count because it looked better. Low
count gives the bland results I posted in p.b.i.
         recursion_limit 5 <--- I have several panes of glass in the scene.
Without a higher recursion limit, the scene gets very dark.
         brightness 1 <-- The Default
         max_sample 2 <-- Increaced for the lights upstairs, which have a
high ambient.
         low_error_factor 1 <-- Tim Nikias' value, again.
         adc_bailout 0.01/20 <-- default, I believe.
         save_file "radios" <--'Nuff said
        #else

      pretrace_start 1 <-- Pretraces set to one for second pass
      pretrace_end   1
      count 1200 <-- count set the same as above.
      recursion_limit 5 <--same as above
      low_error_factor .5 <-- Looking at this again, I realize I never
deleted this. Correct number is below.
      gray_threshold 0.0 <-- Default
      brightness 1.25 <--Looked better this way. The room is a little dark
w/o
      error_bound .8 <-- Value multiplied to smooth out samples
      minimum_reuse .0025 <-- Default
      nearest_count 20 <-- Tim, again
      low_error_factor 1 <-- Same as above
      adc_bailout 0.01/20 <--Default
      load_file "radios" <--'Nuff said
      always_sample off <-- Two pass radiosity
      max_sample 1 <--So I can see the partitions in the lights, now that
the light from them is calculated
     #end
  }


Thanks for your help!

-s
5TF!


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From: stm31415
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 20:10:00
Message: <web.41bb9933420c6eda607ddbe00@news.povray.org>
>
>       minimum_reuse .0025 <-- Default
>


'scuse me. Turns out this value is NOT the default. I reduced it to gain
more
data, and smooth out the effects, so that all that interest in the shadows
I want looks OK.

-S
5TF!


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From: stm31415
Subject: Re: Radiosity: is this appropriate?
Date: 11 Dec 2004 21:45:00
Message: <web.41bbb010420c6edaacced0c50@news.povray.org>
Can anyone tell me what values they use? If mine are *that* far off, maybe I
am texturing improperly.

Thanks, though, for all the help so far. From the reactions, I obviously
don't have *something* right.

-S
5TF!


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From: Christoph Hormann
Subject: Re: Radiosity: is this appropriate?
Date: 12 Dec 2004 05:00:02
Message: <cph4nu$271$1@chho.imagico.de>
stm31415 wrote:
> 
> Well, let me explain why I used them, and hopefully someone can tell me
> where I went wrong.
> 
>  radiosity {
>         #if (pass1)
>          pretrace_start .04    <--- The pretraces, I reduced in size to get
> a little more variation in the colors and shadows of that big, blank far
> wall, by avoinding large sample areas.
>           pretrace_end   .01   <--- See above

Pretrace settings only influence the way samples are taken, you will 
hardy achieve any general change except in artefacts.  The pretrace_end 
should be choosen with respect to the error_bound so the majority of the 
samples are taken during pretrace.  Your value probably is too high.

>          error_bound .1 <-- I reduced the error bound until it looked good.
> Larger is too low quality, and lower changes very little.

Lower error_bound != higher quality!

>          nearest_count 20 <--I was using this because that's what Tim Nikias
> reccomended for 2 pass radiosity. Ensures more even samples, as I
> understand it.

This first of all immensly increases render time and memory use.  And 
your argument does not even mention it increases quality in this case.

>          count 1200 <-- I used a high count because it looked better. Low
> count gives the bland results I posted in p.b.i.

You mostly need a high count because your other settings require it.

>          recursion_limit 5 <--- I have several panes of glass in the scene.
> Without a higher recursion limit, the scene gets very dark.

Transparent surfaces are influenced by max_trace_level but have no 
relation to recursion_limit - this is only relevant for the diffuse 
reflection iteration.  The idea of two pass radiosity is to avoid 
refractive/reflective surfaces in the first pass.

>          max_sample 2 <-- Increaced for the lights upstairs, which have a
> high ambient.

max_sample *limits* the brightness of samples and does not increase it.

>       nearest_count 20 <-- Tim, again

complete nonsense in combination with 'always_sample off'.

>       max_sample 1 <--So I can see the partitions in the lights, now that
> the light from them is calculated

Changing this in the second pass is a possible artefact creator.

Again my recommendation: start with the default and only change settings 
when you see they have the intended effect.

Christoph

-- 
POV-Ray tutorials, include files, Sim-POV,
HCR-Edit and more: http://www.tu-bs.de/~y0013390/
Last updated 23 Sep. 2004 _____./\/^>_*_<^\/\.______


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