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In article <3c0e39ec@news.povray.org>, run### [at] mobilixnet dk
says...
> Of course I haven't tried it, but I think most (maybe all) will impact a
> planet but some might leave the system (that happened in some other tests).
Then you have a problem. They should't be able to do this (unless they
have a high initial speed) because of energy-conservation.
I tried a similar thing (in C, but 2D), and had the problem that some
partices that passed the gravity-source in small dinstance tend to gain a
lot of speed, because the gravity force varies very much in a very small
area, so the simulation gets unaccurate.
Or maybe some kind of "adaptive iteration step length" could help here.
Lutz-Peter
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"Lutz-Peter Hooge" <lpv### [at] gmxde> wrote :
>
> Then you have a problem. They should't be able to do this (unless they
> have a high initial speed) because of energy-conservation.
Um... I am probably the last person to challenge this, but "evaporation"
of an orbital system is pretty common. Energy is conserved, as it is taken
from other objects. Some things slow down and other things speed up.
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"Lutz-Peter Hooge" wrote:
> Then you have a problem. They should't be able to
> do this (unless they have a high initial speed)
> because of energy-conservation.
Sure, but what's considered high initial speed? I think the particles have
high initial speed...
> I tried a similar thing (in C, but 2D), and had the
> problem that some partices that passed the
> gravity-source in small dinstance tend to gain a
> lot of speed, because the gravity force varies very
> much in a very small area, so the simulation gets
> unaccurate.
My particles collide with the planet before that happens.
> Or maybe some kind of "adaptive iteration step length"
> could help here.
Haha, that's completely out of the question with my system. Having each
particle have differently spaced interation steps - that sure would be a
mess, and practically impossible to code into my system...
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Nov 5)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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In article <3c0e58e2$1@news.povray.org>, bde### [at] cflrrcom says...
> Energy is conserved, as it is taken
> from other objects. Some things slow down and other things speed up.
Yep, in reality, but this can't be the case here, because in this
particle system, the particles themselves doesn't influence each
other....
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"Rune" wrote:
> My particles collide with the planet before that happens.
Of course that only applies to this animation, not my system in general.
Because the system is so flexible, it's up to the user to make sure unwanted
effects don't take place.
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Nov 5)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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In article <3c0e5a4a@news.povray.org>, run### [at] mobilixnetdk
says...
> Sure, but what's considered high initial speed? I think the particles have
> high initial speed...
I think, they would escape the system immediately if they had sufficient
energy. I maybe wrong though.
> My particles collide with the planet before that happens.
Perhaps the effect isn't visible at once, but accumulates?
> Haha, that's completely out of the question with my system. Having each
> particle have differently spaced interation steps - that sure would be a
> mess, and practically impossible to code into my system...
Yes, it was just an idea, and probably anyway overkill unless you want to
accurately simulate a solar system :-)
Lutz-Peter
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"Lutz-Peter Hooge" <lpv### [at] gmxde> wrote in message
news:MPG.16787994d47543659896c6@news.povray.org...
> In article <3c0e58e2$1@news.povray.org>, bde### [at] cflrrcom says...
>
> > Energy is conserved, as it is taken
> > from other objects. Some things slow down and other things speed up.
>
> Yep, in reality, but this can't be the case here, because in this
> particle system, the particles themselves doesn't influence each
> other....
Ah, I didn't read that in the previous posts. I assumed that they did
inter-react. If not, you are correct, they either have too high an initial
velocity or he has a problem.
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Rune wrote:
>
> I'm not sure I like what I hear. Are you implying that my particle system
> may not be good enough for NASA to use?
>
It might interest you that NASA once had serious problems with exactly
this problem, but i don't know the precise details, i just heard it
somewhere.
'drift' of the results is a common problem with simulation of such systems
so no need to feel bad about it. ;-)
Christoph
--
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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Lutz-Peter Hooge wrote:
>
> I think, they would escape the system immediately if they had sufficient
> energy. I maybe wrong though.
>
Not necessarily, in a 3 body system they can collide with one of the
masses even if the speed is very high.
Christoph
--
Christoph Hormann <chr### [at] gmxde>
IsoWood include, radiosity tutorial, TransSkin and other
things on: http://www.schunter.etc.tu-bs.de/~chris/
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In article <3C0E5F60.E0C56986@gmx.de>, chr### [at] gmxde says...
> Not necessarily, in a 3 body system they can collide with one of the
> masses even if the speed is very high.
Thats even possible with a two-body-system:
o---> <-O
:-)
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