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.


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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.


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**********************
http://www.oyonale.com
**********************
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> --
> 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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As mentioned to Florian Brucker, here's a link to a better
and more handsome PDF-Version:
http://www.eml.hiroshima-u.ac.jp/member/staff/kin/publications/CA93/wdroplet
.pdf

If you actually do it, remember to comment it the SDL heavily,
so that others might learn from it. I know, you're french, and would
probably comment in french, but I'm german and still try to stick to
english when naming parameters and such, so that most Users might
learn something and understand it very easily...

And from your posts it doesn't look like you're not skilled enough for
english commentary! :-)

Regards,
Tim

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Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

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3e248276@news.povray.org...

> If you actually do it, remember to comment it the SDL heavily,
> so that others might learn from it.

Oh well, some people here are so good at maths that they could probably
implement this in a evening or so [hint, hint ;-)] ...

My only advantage is that Nobel Prize Pierre-Gilles de Gennes (who is cited
a in the paper) works a couple of streets away so I could perhaps kidnap him
and ask for functional, working code...

> probably comment in french, but I'm german and still try to stick to
> english when naming parameters and such, so that most Users might
> learn something and understand it very easily...

I know, I know, even the scenes I don't plan to release are commented in
English now, just in case I have to cut and paste some code in these
groups... Not that I like it but it's better than renaming the variables at
the last minute.

G.

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**********************
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In article <3e23a9eb@news.povray.org>, "KalleK" <kal### [at] gmxde> 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...

Don't. This will not work properly: the ray will never leave the object 
if it goes through an area that was clipped away, and won't enter the 
object properly from the glass side. The correct solution is simpler, 
just overlap the objects.

-- 
Christopher James Huff <cja### [at] earthlinknet>
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG: chr### [at] tagpovrayorg
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In article <3e23f9ed$1@news.povray.org>,
 "Tim Nikias" <tim### [at] gmxde> wrote:

> It "does things"? What does it do? Just curious.

Take a ray entering a droplet for example: it hits the droplet surface 
and gets refracted, and is now inside the droplet. The next surface it 
hits is the glass, so it gets refracted as it should when going from 
water to glass. It is now inside the glass and the droplet. When it hits 
the other droplet surface, *no refraction is done*, but it leaves the 
droplet. (I think it still computes the texture, I'm not sure it should 
though.)
Now the ray has gone through the droplet, been refracted going from 
air/water and water/glass, and is now in the glass, just as it should be.


> Though doing that with blobs is still kinda difficult...

No more so than for any other object. The difficulty is more determined 
by the object you are placing the blobs on.

-- 
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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Why don't you like it? I've heard several rumours about
french people and languages... They like to stick to theirs... ;-)

In some respect, germans are much the same. Some are
really against incorporating english words into the known german
vocabulary. And sometimes, things get messed up. For example,
cell-phones are called "Handy", but ask any american, they
wouldn't know what we're referring to, unless they're told.

About that math-stuff... I think, if I sit down, I could solve it,
though perhaps not strictly by the rules given in the paper. Especially
that modelling part about angles of the water-droplets and such would
be quite difficult, I think.

But right now, I'm not really in the mood to dig into that. There's a lot
of scientific papers floating on my harddrive, waiting to be implemented
in one way or the other... Next week perhaps... ;-)
No, seriously, I do like the idea of this, might be a very useful addition
to lots of realistic scenes. I've actually found some MPEG showing off
what the code is capable of:
http://www.eml.hiroshima-u.ac.jp/member/staff/kin/publications/JVCA
As I'm posting this, the page can't be accessed, don't know why. Perhaps
back online tomorrow.

We'll see who gets to implement this first. That wave-algorithm Rune
and then Christopher Hormann (if I'm not mistaken, was at least a
Christopher :-) implemented was something I wanted to do as well...

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

>
> Oh well, some people here are so good at maths that they could probably
> implement this in a evening or so [hint, hint ;-)] ...
>
> My only advantage is that Nobel Prize Pierre-Gilles de Gennes (who is
cited
> a in the paper) works a couple of streets away so I could perhaps kidnap
him
> and ask for functional, working code...
>
>
> I know, I know, even the scenes I don't plan to release are commented in
> English now, just in case I have to cut and paste some code in these
> groups... Not that I like it but it's better than renaming the variables
at
> the last minute.
>

Post a reply to this message

> Take a ray entering a droplet for example: it hits the droplet surface
> and gets refracted, and is now inside the droplet. The next surface it
> hits is the glass, so it gets refracted as it should when going from
> water to glass. It is now inside the glass and the droplet. When it hits
> the other droplet surface, *no refraction is done*, but it leaves the

I guess you meant "When it hits the other glass surface", cause it makes
no sense if it doesn't refract when exiting the water and entering air.

> droplet. (I think it still computes the texture, I'm not sure it should
> though.)

I think it should compute the texture, since if an object is transparent and
has two sides, POV's rays will be affected by each surface. That's just
the way its implemented and IMHO how I would expect it to behave. If
we'd want 100% realism, we'd probably have to texture it completely
transparent, but add some interior color, like using fade_color and
fade_power or such.

> No more so than for any other object. The difficulty is more determined
> by the object you are placing the blobs on.

You're right about that. It works pretty well for a window made of a single
box, but I'm always thinking "general", to keep things flexible.

--
Tim Nikias
Homepage: http://www.digitaltwilight.de/no_lights/index.html
Email: Tim### [at] gmxde

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