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Hi,
I have a problem when I combine radiosity and transparent objects.
Splotchiness appears behind glass in the second pass.
I use 2 pass radiosity:
1st pass.- No transparency, no reflection, no area_lights, save_radiosity
2nd pass.- transparency, reflection, area_lights, load_radiosity
The parameters are:
#if (RAD)
radiosity {
brightness 1.0 //[1.0]
recursion_limit 3 //[3]
count 800 //[35]
error_bound 0.2 //[1.8]
gray_threshold 0.5 //[0.0]]
pretrace_start 0.05 //[0.08]
pretrace_end 0.01 //[0.04]
nearest_count 15 //[5]
#if(SAVERAD)
save_file "escena.rad"
#else
pretrace_start 1
pretrace_end 1
load_file "escena.rad"
always_sample off
#end
}
#end
I post an image for an example.
Regards,
Joel
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Attachments:
Download 'image.jpg' (459 KB)
Preview of image 'image.jpg'
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I don't know the underlying mechanics of how radiosity works, but I'm
guessing your extra, bouncing rays require more samples in your
reflection/transparency/area lights scene. A few suggestions for your
parameters:
error_bound seems quite low. Try increasing it to 0.5 or 0.8. Your
lighting will be less accurate but you will get smoother, faster
results, and since you are already using regular light sources, the
accuracy shouldn't be an issue.
recursion_limit, try dropping that to two. You'll save some time on the
rendering and your scene may not require the third bounce since you are
using regular light sources and the contrast isn't that high.
count, keep increasing it if you are still getting artifacts. Try going
all the way to 1600. This is why I suggested a higher error_bound and
lower recursion_limit, so that increasing the count wouldn't kill your
render time (too much).
always_sample, turning this off may eliminate some blotchiness. Make
sure you aren't rendering a saved rad file from your reflectionless pass
too.
Skip
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look here:
http://tag.povray.org/povQandT/languageQandT.html#radiosityartifact
perhaps you just don't see them in the first pass because they appear behind
the glass, which is opaque then... follow the instructions in the FAQ.
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Shouldn't you remove the transparent objects when you save radiosity?
otherwise how can light get through them?
--
Tek
http://evilsuperbrain.com
"JSR" <jsr### [at] gmail com> wrote in message
news:web.46383fbb13839e21d8ef73430@news.povray.org...
> Hi,
> I have a problem when I combine radiosity and transparent objects.
> Splotchiness appears behind glass in the second pass.
> I use 2 pass radiosity:
> 1st pass.- No transparency, no reflection, no area_lights, save_radiosity
> 2nd pass.- transparency, reflection, area_lights, load_radiosity
>
> The parameters are:
> #if (RAD)
> radiosity {
> brightness 1.0 //[1.0]
> recursion_limit 3 //[3]
> count 800 //[35]
> error_bound 0.2 //[1.8]
> gray_threshold 0.5 //[0.0]]
> pretrace_start 0.05 //[0.08]
> pretrace_end 0.01 //[0.04]
> nearest_count 15 //[5]
>
> #if(SAVERAD)
> save_file "escena.rad"
> #else
> pretrace_start 1
> pretrace_end 1
> load_file "escena.rad"
> always_sample off
> #end
> }
> #end
>
> I post an image for an example.
>
> Regards,
>
> Joel
>
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"Tek" <tek### [at] evilsuperbraincom> wrote:
> Shouldn't you remove the transparent objects when you save radiosity?
> otherwise how can light get through them?
Either remove the transparent objects completely in the first pass as Tek
suggests, or have them fully transparent as with the second pass (and make
sure recursion_limit is high enough to let the light through properly), or,
if you are using MegaPOV, set the no_radiosity flag on your transparent
objects.
The second option will be the most realistic, but may also be slower.
Nice scene by the way!
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JSR nous apporta ses lumieres en ce 02-05-2007 03:37:
> Hi,
> I have a problem when I combine radiosity and transparent objects.
> Splotchiness appears behind glass in the second pass.
> I use 2 pass radiosity:
> 1st pass.- No transparency, no reflection, no area_lights, save_radiosity
> 2nd pass.- transparency, reflection, area_lights, load_radiosity
>
> The parameters are:
> #if (RAD)
> radiosity {
> brightness 1.0 //[1.0]
> recursion_limit 3 //[3]
> count 800 //[35]
> error_bound 0.2 //[1.8]
> gray_threshold 0.5 //[0.0]]
> pretrace_start 0.05 //[0.08]
> pretrace_end 0.01 //[0.04]
> nearest_count 15 //[5]
>
> #if(SAVERAD)
> save_file "escena.rad"
> #else
> pretrace_start 1
> pretrace_end 1
> load_file "escena.rad"
> always_sample off
> #end
> }
> #end
>
> I post an image for an example.
>
> Regards,
>
> Joel
>
>
> ------------------------------------------------------------------------
>
In the first pass, the glass doors are present and opaque. Result: there is NO
radiosity sampling behind them during that pass, leaving all the sampling to the
second pass.
Suggestion: REMOVE transparent objects during the first pass.
Your count may be to low, increase it some, somewhere from 1000 to 1600.
A low error_bound is good to deepen shadows. Your shadows are almost black. You
probably can increase it a good deal.
Increasing nearest_count to 20 (max value) can help reducing splotchiness.
If you need the extra samples of a small error_bound, using a smaler
low_error_factor can help by gathering more samples during the last pretrace step.
Some of your dark spots may be caused by rays hiting exactly a corner and geting
radiosity samples from "outside" the scene. A very small change in the camera
position can often remove them, or make them change location.
Also, changing the pretrace_start valus may, in some cases, help.
--
Alain
-------------------------------------------------
A husband is what is left of a man after the nerve is extracted.
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Bill Pragnell nous apporta ses lumieres en ce 02-05-2007 17:00:
> "Tek" <tek### [at] evilsuperbraincom> wrote:
>> Shouldn't you remove the transparent objects when you save radiosity?
>> otherwise how can light get through them?
>
> Either remove the transparent objects completely in the first pass as Tek
> suggests, or have them fully transparent as with the second pass (and make
> sure recursion_limit is high enough to let the light through properly), or,
> if you are using MegaPOV, set the no_radiosity flag on your transparent
> objects.
>
> The second option will be the most realistic, but may also be slower.
>
> Nice scene by the way!
>
Beter to leave the coloured transparent objects, radiosity samples passing
trough get coloured. Same for those with non-flat surfaces, change the location
from where the samples are effectively taken. Remove those that are colourless,
thin and flat.
--
Alain
-------------------------------------------------
If That Phone Was Up Your Butt, Maybe You Could Drive A Little Better!
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From: Sabrina Kilian
Subject: Re: Splotchiness with radiosity + transparency
Date: 2 May 2007 21:01:05
Message: <46393451$1@news.povray.org>
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I had a problem with a mirror behind a sheet of glass. Without
radiosity, there were no spots. Turning radiosity on, lots of little
dots between the mirror and glass sheet. The problem in that was diffuse
>0.0 on the mirror surface. That, combined with the glass surfaces,
caused circular little dots. Radiosity settings changed only the size
and locations of the dots in my scene.
I don't know that it's the same problem in your scene, but it's
something else you can look at.
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