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A bug ? I don't know but it is certainly not what was expected. This code
comes straight from Mike's scattering media tutorial and was only modified
by the addition of the sampling type. The results however show something
very strange happening to the lighting in the scene and is nothing like
what one obtains from media in the official version of POV-Ray. I'll post
an example image in the images group for reference sake.
Example code:
/****** start right here ********/
#include "colors.inc"
camera {
location <-10, 8, -19>
look_at <0, 5, 0>
angle 75
}
background { color rgb <0.2, 0.4, 0.8> }
light_source { <0, 19, 0> color rgb 0.5 media_interaction off }
light_source {
<40, 25, 0> color rgb <1, 1, 1>
spotlight
point_at <0, 5, 0>
radius 20
falloff 20
media_attenuation on
}
union {
difference {
box { <-21, -1, -21>, <21, 21, 21> }
box { <-20, 0, -20>, <20, 20, 20> }
box { <19.9, 5, -3>, <21.1, 15, 3> }
}
box { <20, 5, -0.25>, <21, 15, 0.25> }
box { <20, 9.775, -3>, <21, 10.25, 3> }
pigment { color red 1 green 1 blue 1 }
finish { ambient 0.2 diffuse 0.5 }
}
media {
scattering {1, .1 extinction .1}
sample_method 2
samples 10, 100
intervals 6
ratio .99
confidence .999
variance 1/10000
}
/****** finish right here ********/
--
Ken Tyler
1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html
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Increase the intervals, and lower the samples to the same number, e.g. 2,2
3,3 10, 10.
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TonyB wrote:
>
> Increase the intervals, and lower the samples to the same number, e.g. 2,2
> 3,3 10, 10.
I should not have to tweak the code to get acceptable lighting results.
--
Ken Tyler
1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html
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>I should not have to tweak the code to get acceptable lighting results.
Yes, you should. This is not the old media. This is different. It doesn't
work the same. Mike said that this one is only useful for certain effects,
anyway.
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Mike's had a setback with it too, was talking about it Saturday night
at POV-Ray Chat on AOL. He was encountering a totally black media
after hiw most recent compilation. No idea if any relation to
possible other problems but seems something might not be correct in
the code I guess. He'll have to speak for himself, all I'd have to
say is totally wild conjectures (duh).
Bob
TonyB <ben### [at] panama phoenix net> wrote in message
news:37eed529@news.povray.org...
> >I should not have to tweak the code to get acceptable lighting
results.
>
>
> Yes, you should. This is not the old media. This is different. It
doesn't
> work the same. Mike said that this one is only useful for certain
effects,
> anyway.
>
>
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Bob Hughes wrote:
>
> Mike's had a setback with it too, was talking about it Saturday night
> at POV-Ray Chat on AOL. He was encountering a totally black media
> after hiw most recent compilation. No idea if any relation to
> possible other problems but seems something might not be correct in
> the code I guess. He'll have to speak for himself, all I'd have to
> say is totally wild conjectures (duh).
>
> Bob
My point to Tony may not have been altogether clear either. I don't care
right now how the media appears. It is the way the light sources themselves
are acting that I am finding disturbing. I can adjust the media but I cannot
recode the way the light sources are working in the scene.
--
Ken Tyler
1100+ Povray, Graphics, 3D Rendering, and Raytracing Links:
http://home.pacbell.net/tylereng/index.html
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> My point to Tony may not have been altogether clear either. I don't care
> right now how the media appears. It is the way the light sources themselves
> are acting that I am finding disturbing. I can adjust the media but I cannot
> recode the way the light sources are working in the scene.
There really isn't anything going on with the lighting here. What's happening
is that you are specifying a min of 10 samples and a max of 100. Up to the
minimum the new method is being used. The next 90 are being cast in the same
spot (the end of the interval). When it's all averaged out you end up with
bright areas at the end of the interval.
I could simply fix this by using the max samples or ignoring them altogether.
-Mike
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> Mike's had a setback with it too, was talking about it Saturday night
> at POV-Ray Chat on AOL. He was encountering a totally black media
> after hiw most recent compilation.
I got that part fixed. There's something in the code I still don't
understand, as I can't get supersampling to work yet.
At this point I'm thinking of just scrapping backwards compatibility for
now and try to just get it to work the way I want it to. In the meantime
I might update the one I released to add a fix for the problem Ken
pointed out and to change the new keywords.
-Mike
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Good idea.
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I also tried making a variety of modifications to media, including evenly
spaced samples and supersampling, but I couldn't get supersampling to work
properly either. I now know what I was doing wrong. Make sure that when
you super-sample, you give the super-samples less weight in the average.
I.E. if you add a new sample between two existing samples, the new weights
of the existing samples plus the weight of the new sample should still add
up to the sum of the original weights of the two original samples. Ok...
that sounds a lot more confusing than I intended.
-Nathan
Mike <pov### [at] aol com> wrote in message news:37EF0DCB.98DCDE0D@aol.com...
> > Mike's had a setback with it too, was talking about it Saturday night
> > at POV-Ray Chat on AOL. He was encountering a totally black media
> > after hiw most recent compilation.
>
> I got that part fixed. There's something in the code I still don't
> understand, as I can't get supersampling to work yet.
>
> At this point I'm thinking of just scrapping backwards compatibility for
> now and try to just get it to work the way I want it to. In the meantime
> I might update the one I released to add a fix for the problem Ken
> pointed out and to change the new keywords.
>
> -Mike
>
>
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