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From: jmvdvalk
Subject: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 06:58:53
Message: <3cd11bed$1@news.povray.org>
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Beta RC3 / Win98 / 700 Mhz PIII / 128 meg
When rendering with radiosity, the amount of ambient light coming from
objects with a dark pigment, is not what I expected.
With a default finish, the threshold is somewhere around 0.033 for the total
of the color components.
Radiosity quality does not seem to be of any influence, however, increasing
the diffuse factor will decrease the threshold.
The scene shows a horizontal bar with pigment fading from black to
0.1*green.
It should show a smooth linear fade, but has a sawtooth at about 1/3 of the
ramp.
If the light source is removed, no illuminance should remain. However, the
"sawtooth" is still visible.
Can anyone confirm that this is not "expected behavior"?
If this turns out to be a flaw, can anyone confirm that it will be fixed in
the final release of 3.5?
Thanks,
Jan Maarten van der Valk
The scene............
global_settings {
assumed_gamma .5 //make up for the low pigment values (improved
visibility)
radiosity { } //default settings - higher qualities do not affect the
phenomenon
ambient_light 0
}
camera { location -z look_at z }
light_source { -z 1 }
box {
<-.5, 0, 0> <.5, .1, .001>
pigment {
gradient x
color_map {
[0, rgb 0 ]
[1, rgb <0, .1, 0> ]
}
translate -.5*x
}
// finish { diffuse .8 }
}
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From: Thorsten Froehlich
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 08:13:34
Message: <3cd12d6e@news.povray.org>
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In article <3cd11bed$1@news.povray.org> , "jmvdvalk" <jm.### [at] hccnet nl>
wrote:
> Can anyone confirm that this is not "expected behavior"?
Does it work the same way in 3.1?
Thorsten
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From: jmvdvalk
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 09:07:14
Message: <3cd13a02$1@news.povray.org>
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Thorsten Froehlich heeft geschreven in bericht <3cd12d6e@news.povray.org>...
>In article <3cd11bed$1@news.povray.org> , "jmvdvalk" <jm.### [at] hccnetnl>
>wrote:
>
>> Can anyone confirm that this is not "expected behavior"?
>
>Does it work the same way in 3.1?
>
> Thorsten
3.1 renders it fine with option +GR (no sawtooth and after removing light
source no light at all)
Jan Maarten
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From: Kari Kivisalo
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 09:48:16
Message: <3CD143B6.92ED1DAD@luxlab.com>
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This works as expected when ambient is set to 0 or 1.
The error is seen with non-zero diffuse (1). This
happens in MP0.7 too.
global_settings {
assumed_gamma 0.5
radiosity {}
}
camera {location -z look_at 0}
box {
<-.5, -0.1, 0> <.5, .1, 1>
pigment {
gradient x
color_map {
[0, rgb 0 ]
[1, rgb 0.0119*2 ]
}
translate -.5*x
}
finish{diffuse 0 ambient 1}
}
_____________
Kari Kivisalo
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From: jmvdvalk
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 10:41:36
Message: <3cd15020@news.povray.org>
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Kari Kivisalo heeft geschreven in bericht <3CD143B6.92ED1DAD@luxlab.com>...
>This works as expected when ambient is set to 0 or 1.
>The error is seen with non-zero diffuse (1). This
>happens in MP0.7 too.
It happens with zero diffuse as well. In that case it just spans the whole
fade.
xxxxxxxxxxxxxxxxxxxxxxxxx
global_settings {
assumed_gamma .5
radiosity { }
ambient_light 0
}
camera { location -z look_at z }
box {
<-.5, 0, 0> <.5, .1, .001>
pigment {
gradient x
color_map {
[0, rgb 0 ]
[1, rgb <0, .1, 0> ]
}
translate -.5*x
}
finish { diffuse 0 }
}
xxxxxxxxxxxxxxxxxxxxxxxxxx
Jan Maarten
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From: jmvdvalk
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 10:52:29
Message: <3cd152ad@news.povray.org>
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jmvdvalk heeft geschreven in bericht <3cd15020@news.povray.org>...
>
>Kari Kivisalo heeft geschreven in bericht <3CD143B6.92ED1DAD@luxlab.com>...
>>This works as expected when ambient is set to 0 or 1.
>>The error is seen with non-zero diffuse (1). This
>>happens in MP0.7 too.
>
>It happens with zero diffuse as well. In that case it just spans the whole
>fade.
Oops, no it doesn't...
Made a mistake, sorry.
Nevertheless, it seems to me that this is (like you said) an error.
Jan Maarten
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From: Ari-Matti Leppanen
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 12:25:33
Message: <3cd1687d$1@news.povray.org>
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:
: global_settings {
: assumed_gamma 0.5
: radiosity {}
: }
:
: camera {location -z look_at 0}
:
: box {
: <-.5, -0.1, 0> <.5, .1, 1>
: pigment {
: gradient x
: color_map {
: [0, rgb 0 ]
: [1, rgb 0.0119*2 ]
: }
: translate -.5*x
: }
: finish{diffuse 0 ambient 1}
: }
Changing diffuse also moves the edge. Smaller diffuse values push it to
the right until the edge can't be seen. If you increase the amount of
color the edge is visible again eg. rgb <0, 0.1, 0> and diffuse 0.5, rgb
<0, 1, 0> and diffuse 0.05, rgb <0, 10, 0> and diffuse 0.005.
Ari-Matti
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From: Nathan Kopp
Subject: Re: Dark pigments and radiosity produce (too much) ambient light
Date: 2 May 2002 18:42:54
Message: <3cd1c0ee$1@news.povray.org>
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"jmvdvalk" <jm.### [at] hccnetnl> wrote...
> Beta RC3 / Win98 / 700 Mhz PIII / 128 meg
>
> When rendering with radiosity, the amount of ambient light coming from
> objects with a dark pigment, is not what I expected.
Fixed for next beta.
-Nathan
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