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I am experiencing some weird artifacts with radiosity, namely black blotches. I
know this is a pretty standard problem, but all solutions I found recommend
changing the error bound etc which I think I've done correctly yet I still get
the artifacts. I am using povray 3.7.
global_settings { assumed_gamma 1 radiosity { // --- Settings
3 (high quality) ---
pretrace_start 0.08
pretrace_end 0.005
count 400
error_bound 0.01
recursion_limit 1
nearest_count 20
}}
#include "colors.inc" // The include files contain
camera {
location < -100,240,-20>
look_at <0.0,20,0>
//angle 8.7
focal_point <0,20.0>
blur_samples 80
}
sphere{<100,100,0> 20 finish{emission 40} pigment{White} hollow}
plane {
<0, 1, 0>, -3
pigment{color <1,1,1>}
finish { reflection {0.5} ambient 0.0 diffuse 1 specular 0 brilliance 0}
no_reflection
}
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"noam" <nomail@nomail> wrote:
> I am experiencing some weird artifacts with radiosity, namely black blotches. I
> know this is a pretty standard problem, but all solutions I found recommend
> changing the error bound etc which I think I've done correctly yet I still get
> the artifacts. I am using povray 3.7.
>
>
>
>
>
> global_settings { assumed_gamma 1 radiosity { // --- Settings
> 3 (high quality) ---
> pretrace_start 0.08
> pretrace_end 0.005
> count 400
> error_bound 0.01
> recursion_limit 1
> nearest_count 20
> }}
>
>
>
> #include "colors.inc" // The include files contain
>
>
>
>
> camera {
> location < -100,240,-20>
> look_at <0.0,20,0>
> //angle 8.7
> focal_point <0,20.0>
> blur_samples 80
>
> }
> sphere{<100,100,0> 20 finish{emission 40} pigment{White} hollow}
>
> plane {
> <0, 1, 0>, -3
>
> pigment{color <1,1,1>}
> finish { reflection {0.5} ambient 0.0 diffuse 1 specular 0 brilliance 0}
> no_reflection
>
>
> }
Sorry, here's an even simpler working example that reproduces my problem, this
time even using just povray's default config:
#include "rad_def.inc"
global_settings {
radiosity {
Rad_Settings(Radiosity_OutdoorHQ,off,off)
}
}
#include "colors.inc" // The include files contain
camera {
location < -100,240,-20>
look_at <0.0,20,0>
}
sphere{<100,100,0> 20 finish{emission 1} pigment{White} hollow}
plane {
<0, 1, 0>, -3
pigment{color <1,1,1>}
finish { reflection {0.5} ambient 0.0 diffuse 1 specular 0 }
no_reflection
}
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> I am experiencing some weird artifacts with radiosity, namely black blotches. I
> know this is a pretty standard problem, but all solutions I found recommend
> changing the error bound etc which I think I've done correctly yet I still get
> the artifacts. I am using povray 3.7.
Scenes using emissive objects as illumination source are always delicate
to configure.
>
>
>
Try this:
#version 3.7;
//#include "rad_def.inc"
global_settings { assumed_gamma 1
radiosity {
pretrace_start 0.08
pretrace_end 0.005
count 10000 990000
error_bound 0.3
recursion_limit 1
nearest_count 20 3
}}
#default{radiosity{importance 75/10000}}
// count will tend, on average, toward 75 for most of your scene.
#include "colors.inc" // The include files contain
camera {
location < -100,240,-20>
look_at <0.0,20,0>
}
sphere{<100,100,0> 20 finish{emission 10} pigment{White}
radiosity{importance 1}}
// VERY high sampling of your emissive sphere
/*
importance set to allow adaptive sampling.
This allow you to set count to some very large values and keep rendering
speed acceptable
by having most of your scenes objects to have more reasonable sampling
*/
plane {
<0, 1, 0>, -3
pigment{color <1,1,1>}
finish { reflection {0.0} ambient 0.0 diffuse 10 specular 0 }
}
Alain
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Alain <kua### [at] videotron ca> wrote:
> > I am experiencing some weird artifacts with radiosity, namely black blotches. I
> > know this is a pretty standard problem, but all solutions I found recommend
> > changing the error bound etc which I think I've done correctly yet I still get
> > the artifacts. I am using povray 3.7.
> Scenes using emissive objects as illumination source are always delicate
> to configure.
> >
> >
> >
>
> Try this:
>
> #version 3.7;
>
> //#include "rad_def.inc"
> global_settings { assumed_gamma 1
> radiosity {
> pretrace_start 0.08
> pretrace_end 0.005
> count 10000 990000
> error_bound 0.3
> recursion_limit 1
> nearest_count 20 3
> }}
>
> #default{radiosity{importance 75/10000}}
> // count will tend, on average, toward 75 for most of your scene.
>
> #include "colors.inc" // The include files contain
>
> camera {
> location < -100,240,-20>
> look_at <0.0,20,0>
>
>
> }
> sphere{<100,100,0> 20 finish{emission 10} pigment{White}
> radiosity{importance 1}}
> // VERY high sampling of your emissive sphere
> /*
> importance set to allow adaptive sampling.
> This allow you to set count to some very large values and keep rendering
> speed acceptable
> by having most of your scenes objects to have more reasonable sampling
>
> */
> plane {
> <0, 1, 0>, -3
>
> pigment{color <1,1,1>}
> finish { reflection {0.0} ambient 0.0 diffuse 10 specular 0 }
>
>
> }
>
>
>
> Alain
Thanks, Alain, that showed some improvement. However I am still getting weird
artifcats, although more subtle ones. Here is a scene with your suggested
improvement, however you can still see black rings on the halo of the sphere
across the plane. I feel like I am missing something in this radiosity
buisness..
global_settings { assumed_gamma 1
radiosity {
pretrace_start 0.08
pretrace_end 0.005
count 10000 990000
error_bound 0.3
recursion_limit 1
nearest_count 20 3
}}
#default{radiosity{importance 75/10000}}
#include "colors.inc" // The include files contain
camera {
location < -100,40,-20>
look_at <0.0,20,0>
}
sphere{<100,60,0> 20 finish{emission rgb<1,1,1>} pigment{White} hollow
radiosity{importance 1}}
plane {
<0, 1, 0>, -3
pigment{color <1,1,1>}
finish { reflection 0.5 ambient 0.0 diffuse 1 specular 0 phong 1 }
no_reflection
}
Post a reply to this message
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> Thanks, Alain, that showed some improvement. However I am still getting weird
> artifcats, although more subtle ones. Here is a scene with your suggested
> improvement, however you can still see black rings on the halo of the sphere
> across the plane. I feel like I am missing something in this radiosity
> buisness..
I once had a similar issue with horrible black circles inside a bit of
furniture I was modelling. That's when someone introduced me to mcpov -
I've never looked back.
mcpov can be found easily via Google, it's an unbiased patch for POV
v3.6. That means the resulting render always tends to *exactly* the
physically correct value over time, no need to fiddle with any radiosity
parameters or worry about artefacts.
The main downsides are that you can't use any new v3.7 features,
including multi-core rendering (so you need to run several instances and
then average the results), and that you cannot use point light sources,
you need to use physical geometry as light (not such a big issue as it
sounds). There's also a minor bug with the brightness of pigments, but
that is easy to compensate for in your code.
Hopefully there will be an unbiased patch for v3.7 soon - I think
someone is working on it... :-)
Post a reply to this message
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>
> Thanks, Alain, that showed some improvement. However I am still getting weird
> artifcats, although more subtle ones. Here is a scene with your suggested
> improvement, however you can still see black rings on the halo of the sphere
> across the plane. I feel like I am missing something in this radiosity
> buisness..
>
> global_settings { assumed_gamma 1
> radiosity {
> pretrace_start 0.08
> pretrace_end 0.005
> count 10000 990000
> error_bound 0.3
> recursion_limit 1
> nearest_count 20 3
Try using a larger second parameter here. It may help.
> }}
>
> #default{radiosity{importance 75/10000}}
>
> #include "colors.inc"
>
> camera {
> location < -100,40,-20>
> look_at <0.0,20,0>
>
>
> }
> sphere{<100,60,0> 20 finish{emission rgb<1,1,1>} pigment{White}// hollow
> radiosity{importance 1}}
>
> plane {
> <0, 1, 0>, -3
>
> pigment{color <1,1,1>}
> finish { reflection 0.5 ambient 0.0 diffuse 1 specular 0 phong 1 }
> no_reflection
>
>
> }
>
>
Your emissive sphere don't need the hollow modifier as it don't contain
any media.
Try using a smaller value for the radiosity's adc_bailout. It dafault to
0.01/2 (or 0.005).
Try something like 0.003 or less.
It's a parameter that's often overlooked and can make a huge difference
when you use emissive objects to illuminate your scene.
Alain
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