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> Any ideas?
Hi Tim!
Maybe, you can tinker with clipped_by, to clip the surface of the drop which
would contact the window. I don't know wether the ray remembers the ior of
the object it currently is in or not. But if it's so, the ray would go from
1.33 straight into 1.45. which should be right...
Hope could help
Kalle
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On Tue, 14 Jan 2003 07:10:48 +0100, "KalleK" <kal### [at] gmx de> wrote:
>Maybe, you can tinker with clipped_by, to clip the surface of the drop which
>would contact the window. I don't know wether the ray remembers the ior of
>the object it currently is in or not. But if it's so, the ray would go from
>1.33 straight into 1.45. which should be right...
Hey Kalle, that's *extremely* neat - did you try it? It does sound
plausible...
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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That's what I'm currently doing, but I'm not sure
if it works as we think it does. As far as I understand
the raytracing technique, POV will stay with ior 1.45 from
the glass until it hits the surface of the water, and gets
refracted the way it should when exiting a 1.33 ior to
1.00 ior (water to air). But I'm not too sure about that,
and also no quiet sure how I should test that...
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
>
> >Maybe, you can tinker with clipped_by, to clip the surface of the drop
which
> >would contact the window. I don't know wether the ray remembers the ior
of
> >the object it currently is in or not. But if it's so, the ray would go
from
> >1.33 straight into 1.45. which should be right...
>
> Hey Kalle, that's *extremely* neat - did you try it? It does sound
> plausible...
>
>
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It "does things"? What does it do? Just curious.
Though doing that with blobs is still kinda difficult...
Instead of clipping, I'd have to difference it away
position it slightly inside the window... Pretty tracing
intensive, hu? I'll try and look what happens. Thanks
for the suggestion though,
Tim
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
>
> > Most of the time, us POVers leave a little gap between two transparent
> > surfaces in order to avoid coincident surfaces. But when refracting
rays,
> > the effect taking place is different as opposed to two surfaces touching
> > each other.
>
> Overlap them a bit. POV does things so that refraction is handled
> correctly in this case. The gap method simulates an air gap.
>
> Designing the textures properly also helps. I usually use perfectly
> transparent textures and use interior attenuation or media to provide
> any coloration.
>
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You're definitely right about placing the droplets.
I've written a small include, which scatters droplets
randomly across an area (the whole thing was designed
so far only for windows), and also creates "trails":
At one spot, it starts, and moves downward (a little
randomly moving towards right or left), and leaves
very small droplets on the way, and at the end, a big droplet.
Just like those drops that get big enough to flow down.
I've uploaded a zoomed-version on the window,
http://www.digitaltwilight.de/no_lights/rain_1.jpg
Its 100kb, but shows how the results look so far. I'm
fiddling a bit with size and numbers to see if I can
get something near-realistic with this method.
I guess Rune's Particle System won't be of use, cause
it doesn't have particle-particle-interaction, and that
would be what droplets on windows are screaming for.
Perhaps I'll try to create an include file for windows, but
doing it with curved survaces and other objects... Way
too difficult. Got to have a running particle-system to do
that...
But near-realistic isn't too bad. Its all about the looks.
How did you place those droplets of yours? Using trace?
Though some look like the gravitational-pull is actually
affecting the droplet. How'd you do that?
Regards,
Tim
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
>
> Can't help, I've had this little problem for years and I was never able to
> solve it properly. Nothing I tried seemed to work as it should. See :
> http://www.oyonale.com/ldc/images/abeillesdetail2.jpg
>
> The main issue, though, is less the surface problem than the distribution
of
> the droplets themselves. Ideally, their position should be the product of
a
> dynamic process, so that simple random positionning always seems wrong.
> Perhaps Rune's particle system could help, I don't know. Blobs doesn't
> behave like real water either, which is another problem.
>
> G.
>
> --
> **********************
> http://www.oyonale.com
> **********************
> - Graphic experiments
> - POV-Ray and Poser computer images
> - Posters
>
>
>
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Using google this came up when looking for
"water droplets simulation":
http://www.cs.unc.edu/~lin/COMP259/LEC/29b.ppt
Its pretty interesting and perhaps, when I get the time to
understand it, I'll implement it. Could be useful, at least
for meshes (and windows can easily be done with
meshes).
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
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3e240121$1@news.povray.org...
> I've uploaded a zoomed-version on the window,
> http://www.digitaltwilight.de/no_lights/rain_1.jpg
Looks like a good start. Perhaps the droplets should be more homogeneous in
shape, though it depends on whether it's still raining or not. Here are some
reference images if you haven't got them.
http://www.danheller.com/images/Italy/Tuscany/rain-window-big.jpg
http://www.pacamera.com/memberGalleries/ammac/rainWindow.jpg
http://www.sengers.ch/special/tropfen.jpg
> How did you place those droplets of yours? Using trace?
> Though some look like the gravitational-pull is actually
> affecting the droplet. How'd you do that?
The trouble is that the code isn't commented...
From what I understand of it, it first creates a grid of droplets in a u,v
plane, because I had observed that in real life dew droplets are somehow
organised and not 100% random (it's different from the rain-beated window
then). The macro is given attractor points that draw droplets to them
(droplets far from the attractor are smaller), with some gentle
function-based displacement. This allows "lines" of droplets of decreasing
size to be created (it's more visible here
http://www.oyonale.com/ldc/images/abeilles.jpg). It's far from perfect but
100% random positionning was really unrealistic.
The u,v positions and sizes of the droplets are stored in arrays and are
then wrapped around the object (a simple cylinder in this case) as a single
blob.
About the gravitational pull, I remember doing it but I can't find it in the
code so perhaps it's just luck...
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
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hey guys
> http://www.cs.unc.edu/~lin/COMP259/LEC/29b.ppt
can you tell me which app i have to use to view that file? powerpoint fails
(normaly uses .ppt, didn't think it would fit either), but google, wotsit ?
co just give powerpoint as target application...
thanks:florian
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3e24041e@news.povray.org...
> http://www.cs.unc.edu/~lin/COMP259/LEC/29b.ppt
>
> Its pretty interesting and perhaps, when I get the time to
> understand it, I'll implement it. Could be useful, at least
> for meshes (and windows can easily be done with
> meshes).
Thanks ! It looks very interesting indeed. I'll have a look at it too, but I
haven't done this kind of math since 1986... It seems feasible in POV-Ray
SDL and could give very nice results.
G.
--
**********************
http://www.oyonale.com
**********************
- Graphic experiments
- POV-Ray and Poser computer images
- Posters
> --
> Tim Nikias
> Homepage: http://www.digitaltwilight.de/no_lights/index.html
> Email: Tim### [at] gmxde
>
>
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It worked fine with Powerpoint for me. Perhaps you've
got the wrong Version?
Here's something that looks much better, and covers the same
topic (I guess its actually the same, though the PPT was the
presentation part...)
http://www.eml.hiroshima-u.ac.jp/member/staff/kin/publications/CA93/wdroplet
.pdf
--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde
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