Well, luckily I haven't got anyone around me who smoke, so I haven't
really studied any cigarette smoke in details, but if it is anything
like the smoke that comes when you blow out a match or a candle, then
maybe the smoke in this animation could go for cigarette smoke.

Well, obviously from the above, I need a lot of feedback to know if I'm
on the right track... ;)

It's supposed to be a demo scene for my particle system, which by the
way is in the beta testing stage if anyone missed my message in
povray.general.

The animation should be viewed with a gamma of at least about 1.8 to
look good.

Maybe you could compare this animation to the one at the address below,
and tell me which is more realistic and why.
http://www.studenter.hb.se/~arch/smokegen/anims/ashtray.avi
It's from the SmokeGen page:
http://www.studenter.hb.se/~arch/smokegen/smokegen.htm

Rune
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Attachments:
Download 'cigsmoke1.mpg' (305 KB)

From my onw (big) experience with cigarette smoke, it is very realistic. 

  But wait... let me burn one... hmmmm... 

  Seems that the real one is a bit more chaotic, but stays "straight" 
during a while, before the turbulence starts. Anyhow, it's definitely a 
very good simulation. 

-- 
Jaime Vives Piqueres

La Persistencia de la Ignorancia
http://www.ignorancia.org

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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3cdfc63f@news.povray.org...
> Well, luckily I haven't got anyone around me who smoke, so I haven't
> really studied any cigarette smoke in details, but if it is anything
> like the smoke that comes when you blow out a match or a candle, then
> maybe the smoke in this animation could go for cigarette smoke.

    Well, as a non-smoker, I can't see why you would bother making cigarette
smoke out of something so cool.

    As a hundred more interesting uses I think it is very good. It misses
some of the granularity that smoke sometimes has, but maybe that's the
scale. And it seems to go chaotic very quickly. In a still room I would
expect it to stream a little longer.

    What I would like to see is the kind of double spiral that incense in a
still room sometimes makes... I've seen that go up 3-4 feet before almost
exploding into turbulence.

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Neither I have studied smoke, but here are some guesses:

Your animation:
- Thickness of smoke increases it's brightness. Is this realistic?
- Smoke seems to go upwards a bit too fast.

Smokegen animation:
- Far too thin line of smoke.

Nice to see your system moves to beta stage!  :o)

Regards,
Hugo

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Bill DeWitt wrote:
>     Well, as a non-smoker, I can't see why you would
> bother making cigarette smoke out of something so cool.

Err, thanks! ;)

Any ideas what else I could make it into?
[reading down further]
Ah, incense. Any other ideas, just so I have something more to choose
from? :)

> It misses some of the granularity that smoke
> sometimes has, but maybe that's the scale.

I can try to make it more grainy...

> And it seems to go chaotic very quickly. In a still
> room I would expect it to stream a little longer.

Hmm.

> What I would like to see is the kind of double spiral
> that incense in a still room sometimes makes... I've
> seen that go up 3-4 feet before almost exploding into
> turbulence.

As always, it difficult to precisely visualize for my inner eye what
something looks like from a written description, but I can give it a
try.

Anyway, I wonder what it is that causes the turbulence to happen in such
a sudden way...

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:  http://rsj.mobilixnet.dk (updated Apr 14)
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Jaime Vives Piqueres wrote:
> From my onw (big) experience with cigarette smoke,
> it is very realistic.

Weee... :)

>   But wait... let me burn one... hmmmm...

I take no responsibility for that. ;)

>   Seems that the real one is a bit more chaotic,
> but stays "straight" during a while, before the
> turbulence starts.

That's what Bill said too. I'll have to try to make it do that.

> Anyhow, it's definitely a very good simulation.

Thanks!

The good thing is that it parses and renders very fast because only very
few particles are used, and no media... :D

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:  http://rsj.mobilixnet.dk (updated Apr 14)
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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3cdfc63f@news.povray.org...

Very convincing start.
As for criticism, the smoke shouldn't disappear (at least it seems that way
in the anim) but rather dissipate and spread out (until it loses visibility)

-tgq

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Rune wrote:
> 
> Well, luckily I haven't got anyone around me who smoke, so I haven't
> really studied any cigarette smoke in details, but if it is anything
> like the smoke that comes when you blow out a match or a candle, then
> maybe the smoke in this animation could go for cigarette smoke.
> 
> Well, obviously from the above, I need a lot of feedback to know if I'm
> on the right track... ;)
> 
> [...]

As Bill and Jaime pointed out the smoke moving straight upwards and
getting turbulent after some way is a classical effect. When you model it
mathematically this has to do with the characteristic length getting
longer and at some point the flow is reaching a critical rayleigh number
and changing from laminar to turbulent (from memory, not sure if totally
correct).

Christoph

-- 
POV-Ray tutorials, IsoWood include,                 
TransSkin and more: http://www.tu-bs.de/~y0013390/  
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______

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Hugo wrote:
> - Thickness of smoke increases it's brightness.

Actually it doesn't, but it probably doesn't decrease in brightness as
much as it should.

> - Smoke seems to go upwards a bit too fast.

I agree.

> Nice to see your system moves to beta stage!  :o)

You're welcome to help testing it if you want. "Testing" also means to
make your own scenes and animations... :)

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:  http://rsj.mobilixnet.dk (updated Apr 14)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
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Rune wrote:
> 
> 
> Anyway, I wonder what it is that causes the turbulence to happen in such
> a sudden way...
> 
> Rune
> --

Probably inversion, a layer of warm air on top of a colder
layer.

Nice animation BTW, Rune but my first reaction is similar to
Bill's; it would be great if you could see the nice little
'curlies' you see in incense (haven't looked at cigarette smoke
very closely). I have no idea how you would get this effect, but
I'm impressed already.

Remco

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