>
http://www.math.duke.edu/education/ccp/materials/diffcalc/raindrop/rain1.html
> That's partly chinese for me though :p

Well, actually, that's algebra... :-)

Still, those links explain a more or less accurate particle system to create
raindrops, e.g. terminal velocity (the velocity after which air resistance
stops the raindrop from getting any faster) in relation to it's size,
gravity in relation to it's mass, etc. What Tim is doing here though is
completely different and thus the formulae aren't really applicable (always
wanted to use that word with sense :-).

Still, if he'd switch to a function, it might be possible to transform the
pattern for the rain-media to look slightly curved... (Just hinting at
something, won't dive deeper into this...)

Regards,
Tim

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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No, I don't think I saw that in the FAR. However, if I couldn't see out, how 
could they see in? :)

- Grim

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GrimDude wrote:
> As often seen from below a cloud...
> 
> The rain seems to disappear as you look down upon it, yet from below it is 
> very visible. Canopy defrost cleared this up.
> 
> - Grim 
> 
> 
> 

Great pic. Care to share the scene-file? ;-)

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"Tim Nikias" <JUSTTHELOWERCASE:timISNOTnikias(at)gmx.netWARE> wrote:
> I'd rather say because the drops get moved by wind and the further down you
> get, the further they have been moved from their original path.
> 2 cents. :-)

Not sure I follow your point; isn't that true for a linear translation as
well?

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Renderdog wrote:
> Very dramatic, beautiful clouds! Striking!
> This would make a wonderful print all by itself.
> 
> FWIW, I remember distant rain seems to curve more as it
> nears the ground, maybe because the drops are smaller?
> The straight line rain caught my eye as unnatural, but I'm
> not sure.
> 
> Also, rain usually appears darker, I guess because it's drops
> of water, not vapor.
> 
> 
Rain don't fall straight because the wind at the cloud level is not the same speed and
often not the 
same direction as that at ground level. Sometimes, rain can make "S" and spiraling
curves.
Acording to my perseption, rain columns look darker, even when lit by bright lateral
sun. Snow 
columns are bright when lighted and go whider and whider the lower you go.

Alain

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> Not sure I follow your point; isn't that true for a linear translation as
> well?

It depends entirely on the wind. Generally, wind *never* moves with the same
velocity and in the same direction no matter the altitude. Also, a raincloud
moves further while it drops the rain, so the "youngest" raindrops should be
directly underneath the cloud whereas "older" drops should be were the
raincloud was before. I'm not sure how much increase in speed a raindrop
acquires during the drop, so maybe that can be omitted from the
calculations.

Basically, just add the chaotic nature of, well, nature, and you should get
why rain can't drop in a straight line (at least not diagonally, a straight
drop *might* be possible with no wind at all...).

-- 
"Tim Nikias v2.0"
Homepage: <http://www.nolights.de>

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news:41dee5ca@news.povray.org...
> No, I don't think I saw that in the FAR. However, if I couldn't see out,
how
> could they see in? :)
>
> - Grim
>
Oh yes of course! :)

Marc

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The color of the light is great and the shadow/lighting effects you're
getting are really nice. I still think the cloud needs more samples; make
sure you're using aa_depth and aa_threshold well to minimize calculation.

> I'm finding that though media can be incredibly frustrating, slow and the
> desired effect illusive, that I am enjoying the challenge. So...while my
> progress has been slow, please bear with me.

Media is difficult to learn, but generally worth the time.

 - Slime
 [ http://www.slimeland.com/ ]

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Wow, I post a message before I leave for work and come home to find all
these responses. That is what I call support and encouragement. I see
comments form a lot of people that I very much respect...real artists with
POV and my head swells.

Here are a few answers to questions that came up...

Q: How long did it take to render?
A: The attached image took 2h 47m using my P4 3Ghz with 1G of RD ram

Q: is the light colored?
A: The sky and light are generated using Jaime Vives Piqueres' i_sky.inc
file. This takes advantage of his lighting system.

Q: Will you make the code public? I certainly will, though I will probably
offer the code to Jamie first as it is in effect an extension of his
i_cumulus.inc file.


Again, thank you for all of the comments & I will finish this part of the
project as soon as I can. Perhaps I should go ahead and render a landscape
with the clouds in place next.

Tim

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Attachments:
Download 'cloud-test-3b.jpg' (88 KB)

Preview of image 'cloud-test-3b.jpg'

My impression is that rain should always be "dark cloud" colored, even if 
the cloud is "white".

"Tim McMurdo" <jod### [at] wohrrcom> wrote in message 
news:web.41de8f1c45ddce7aacb32c570@news.povray.org...
>I apologize for taking so long to get back to the group on this project.
> However, like a lot of people, some really enjoyable holidays interfered
> with my work.
>
> I was finally able to get an angled rain column under the cloud. I'm still
> working on the quality of the media its self as well as the shape of the
> clouds. The clouds are being randomly generated using parameters set by 
> the
> user. Some of the clouds now have become massive. I picked this particular
> one because it fit the screen.
>
> I'm finding that though media can be incredibly frustrating, slow and the
> desired effect illusive, that I am enjoying the challenge. So...while my
> progress has been slow, please bear with me.
>
> Tim
>


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