In article <3a983257@news.povray.org>, "Rune" <run### [at] inamecom> 
wrote:

> > Huh? Water normally doesn't float in air...
> 
> When water is below 100 degrees Celsius / 212 degrees Fahrenheit it 
> falls. When it is above, it rises. The "threshold" is at 100 degrees 
> Celsius, not at the temperature of the environment. So the "rule" 
> does not apply to water, not always anyway.

Uh, water boils above 100C. This is phase change, not convection. My 
patch doesn't simulate phase changes. (well, it might, if you use 
inter-particle forces and simulate temperature change by changing the 
velocity of the particles, but it has nothing to do with the temperature 
feature of atmospheric particles)


> > The reason convection happens is the density difference between one 
> > mass of air, and the surrounding air. The density is affected by 
> > the temperature, which will cause a warmer mass of air to rise.
> 
> But the particles themselves are not air, right? They just drift 
> around with the air surrounding them. So if smoke is surrounded by 
> hot air, it will drift upwards along with the air. However, all this 
> only applies to materials that have densities very close to the 
> density of air (like smoke). It doesn't apply to many other materials 
> such as cool water which does not normally drift along with air, even 
> if its temperature is higher than the environment temperature.

The particle system doesn't simulate the interactions of different kinds 
of fluids yet. The atmospheric particles simply assume the environment 
has a very similar density when at the same temperature. And as I said 
before, it doesn't do phase change, so you can't simulate the boiling 
off of water into steam which then rises into the air with a single 
group of particles, you will have to use separate particles for the 
liquid water and for the steam, maybe separate systems.
I plan on eventually giving each particle a density value, along with 
support of multiple fluid types.


> Since the temperature feature does not apply to all uses of the 
> system, can it be turned off?

It only applies to atmospheric particles.

-- 
Christopher James Huff
Personal: chr### [at] maccom, http://homepage.mac.com/chrishuff/
TAG: chr### [at] tagpovrayorg, http://tag.povray.org/

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