In article <3a98066b@news.povray.org>, "Rune" <run### [at] inamecom> 
wrote:

> But what if the object moves a greater distance between two 
> calculation frames than that certain distance you mentioned? And what 
> if the surface movement is not caused by a transformation but by - 
> say an isosurface with a varying function?

That would still be a problem. I'll probably add a feature to kill 
particles that end up inside an environment object, so at least time 
won't be wasted processing them.


> I have never understood what use the temperature feature is. What can 
> it be used to simulate?

Mainly convection and the effects of smoke rising and cooling.


> From the documentation:
> > As the simulation goes on, particles will tend toward the
> > temperature of their environment. Particles hotter than
> > their environment will tend to go against gravity and float,
> > colder particles will sink.
> 
> I don't see the logic in this. It has noting to do with reality. Hot 
> water doesn't float just because it's hotter than the air around it. 

Huh? Water normally doesn't float in air...


> The temperature at which it begins to float is much higher than the 
> temperature of the environment. In fact, the temperature of the 
> environment seems to be completely irrelevant.

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. And there is 
no threshold of temperature difference below which it won't happen. It 
can be on the order of a couple degrees, which is why we have weather.


> And wouldn't your system end up in a state where the particles 
> neither sink nor float?

It will, eventually, if you have no heat sources or emitters of 
unusually hot or code particles. In the same way that smoke will 
eventually disperse throughout a room.

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

<><

Post a reply to this message