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> Is there any way to implement materials that blur the image behind them?
>
> The degree of blur should be related to the path length of light passing
> through a material so surface distortions won't work right.
Don't know if it hits some of pov's limitations, but:
Instead of using a material you might intersect your object with another one.
This second object is glass with bubbles inside, maybe some noise isosurface
or something like that.
In that way the ray will be distorted whenever it passes a bubble and that
will happen more times on thicker parts of the "material".
--
merge{#local i=-11;#while(i<11)#local
i=i+.1;sphere{<i*(i*i*(.05-i*i*(4e-7*i*i+3e-4))-3)10*sin(i)30>.5}#end
pigment{rgbt 1}interior{media{emission x}}hollow}// Mark Weyer
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In article <3f713be4@news.povray.org>,
Lutz-Peter Hooge <lpv### [at] gmx de> wrote:
> > Chris has the right idea... what I'm looking for is a material that blurs
> > the image more if the ray has to pass through a lot of the material rather
> > than just a tiny bit.
>
> What real-life material does this?
> IMHO blurring normally only occurs on surfaces.
Very wrong. Every transparent material does this, but with very clear
materials the interior scattering is insignificant. Examples of where it
is significant: smoke, fog, clouds, milk, translucent materials such as
milky glass, marble, flesh. Glass with lots of microscopic bubbles in
it. In most of these, the light is scattered almost evenly in all
directions, so you don't perceive it as a blur, which would require
scattering at a relatively small angle to the original direction. You
could construct such a material easily the same way you would simulate
it in POV, by stacking thin layers of a blurring material. (With
air-gaps or alternating layers of different ior.)
--
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/
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Christopher James Huff <cja### [at] earthlinknet> wrote:
> smoke, fog,
What you get here is a rather sharp image with a halo
(the blurred image) around it. You don't get this result with
the POV-blurring techniques.
Milk etc is almost opaque, so you don't see any blurring.
If you mix it with a lot of water, so you can see through it, the
blurring becomes insigificant again (I just tested it).
> it. In most of these, the light is scattered almost evenly in all
> directions, so you don't perceive it as a blur,
IMHO if you don't perceive it as blur, it isn't blur, at least
the context of graphics.
Lutz-Peter
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In article <web.3f70fc1178c6ab46be419860@news.povray.org>,
"Kevin" <kev### [at] dukeedu> wrote:
> I agree that to do this the right way would be really expensive, but a quick
> way around it might be to determine the length of the ray that passes
> through the material and then set the local blur size (for that ray) to
> some function of the path length.
This would be possible, though it wouldn't be very close to the real
effect.
> Hmmm.... maybe if you could define a gradient of the normal bump sizes you
> could simulate this effect.. or by playing with normal maps... I'll have to
> fiddle with that.
It would only look right from one direction.
--
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
http://tag.povray.org/
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Christopher James Huff wrote:
>In article <web.3f70fc1178c6ab46be419860[at]news.povray.org>,
> "Kevin" <kev### [at] dukeedu> wrote:
>
>> I agree that to do this the right way would be really expensive, but a quick
>> way around it might be to determine the length of the ray that passes
>> through the material and then set the local blur size (for that ray) to
>> some function of the path length.
>
>This would be possible, though it wouldn't be very close to the real
>effect.
>
>
>> Hmmm.... maybe if you could define a gradient of the normal bump sizes you
>> could simulate this effect.. or by playing with normal maps... I'll have to
>> fiddle with that.
>
>It would only look right from one direction.
>
>Christopher James Huff <cja### [at] earthlinknet>
>http://home.earthlink.net/~cjameshuff/
>POV-Ray TAG: chr### [at] tagpovrayorg
>http://tag.povray.org/
>
I'm beginning to think that I'm just being obsessive-compulsive here. Based
on some of the previous discussion about real materials I would have to
come to the conclusion that the number of places that this effect is
actually noticable is pretty small. I think for my purposes the surface
blur will work fine.
Thanks
Kevin
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Are you looking to simulate translucent materials, as opposed to transparent
materials? I normally bring in a scattering media in those circumstances.
"Mark Weyer" <wey### [at] informatikuni-freiburgde> wrote in message
news:3F7### [at] informatikuni-freiburgde...
> > Is there any way to implement materials that blur the image behind them?
> >
> > The degree of blur should be related to the path length of light passing
> > through a material so surface distortions won't work right.
>
> Don't know if it hits some of pov's limitations, but:
>
> Instead of using a material you might intersect your object with another
one.
> This second object is glass with bubbles inside, maybe some noise
isosurface
> or something like that.
> In that way the ray will be distorted whenever it passes a bubble and that
> will happen more times on thicker parts of the "material".
>
>
> --
> merge{#local i=-11;#while(i<11)#local
> i=i+.1;sphere{<i*(i*i*(.05-i*i*(4e-7*i*i+3e-4))-3)10*sin(i)30>.5}#end
> pigment{rgbt 1}interior{media{emission x}}hollow}// Mark Weyer
>
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> Are you looking to simulate translucent materials, as opposed to transparent
> materials? I normally bring in a scattering media in those circumstances.
1. I am not looking into anything, I just wanted to help Kevin.
2. I am not sure enough about the difference in English terms such as
transparent and translucent. In case of doubt I meant the same as Kevin did.
3. Scattering media seem to be a good idea. Less prone to reach pov's
limitations, simpler to set up and maybe even quicker.
--
merge{#local i=-11;#while(i<11)#local
i=i+.1;sphere{<i*(i*i*(.05-i*i*(4e-7*i*i+3e-4))-3)10*sin(i)30>.5}#end
pigment{rgbt 1}interior{media{emission x}}hollow}// Mark Weyer
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On Tue, 30 Sep 2003 12:25:50 +0200, Mark Weyer
<wey### [at] informatikuni-freiburgde> wrote:
>2. I am not sure enough about the difference in English terms such as
> transparent and translucent. In case of doubt I meant the same as Kevin did.
A translucent material transmits light diffusely like frosted glass. A
transparent material transmits light so that objects or images can be seen as if
there were no intervening material.
Regards
Stephen
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