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It's an amazing accomplishment.
I'm "bothered" by the ball hitting the floor and then bouncing clear out of
the tub.
Perhaps you really mean viscosity rather than surf tension?
Have you seen Stoke's Law?
http://www.science.ubc.ca/~geol256/notes/ch7_sedmov_intro.html
http://www.phys.virginia.edu/classes/152.mf1i.spring02/Stokes_Law.htm
"Christoph Hormann" <chr### [at] gmx de> wrote in message
news:3CE291FC.E1C0909C@gmx.de...
> The second one is with balls lighter than water (800 kg/m^3), the balls
> floating leads to quite some problems as you can see. The water
> disturbance, although speed dependant meanwhile, is still too strong and
> there is no good representation for water surface tension.
>
> Does anyone know a good method for modeling water surface tension? I right
> now only use a simple model that slows down the balls according to the
> energy required for increasing the (flat) surface area, but there probably
> are other important effects that are not covered by this.
>
> Apart from that i added realistic calculation of drag in water and air, i
> also modeled friction during the environment collisions, but without
> rotation this does not really improve realism much. And the animations
> are in real time now.
>
> Christoph
>
> --
> POV-Ray tutorials, IsoWood include,
> TransSkin and more: http://www.tu-bs.de/~y0013390/
> Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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See also:
http://sis.agr.gc.ca/cansis/glossary/stokes_law.html
and what I mean is that your viscosity is way too low.
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"Greg M. Johnson" wrote:
>
> It's an amazing accomplishment.
Thank you.
> I'm "bothered" by the ball hitting the floor and then bouncing clear out of
> the tub.
>
> Perhaps you really mean viscosity rather than surf tension?
No, i mean surface tension. Drag is already modelled correctly although i
was surprised by the effect not being very strong too. I use a kinematic
viscosity of 1e-6 m^2/s which seems a reasonable value for water. Maybe i
should change to some kind of oil...
About that ball: don't forget the balls in that animation are fairly
light, the surface tension effect is fairly strong in means of bodies
sticking to the surface in such situations. Without it the balls are
simply jumping back.
> Have you seen Stoke's Law?
> http://www.science.ubc.ca/~geol256/notes/ch7_sedmov_intro.html
> http://www.phys.virginia.edu/classes/152.mf1i.spring02/Stokes_Law.htm
Yes, this is what i use.
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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"Greg M. Johnson" wrote:
>
> See also:
> http://sis.agr.gc.ca/cansis/glossary/stokes_law.html
> and what I mean is that your viscosity is way too low.
That page does not give a value for water, but a formula for terminal
velocity isn't useful anyway since buoyancy prevents the balls from
sinking.
I have my value from:
http://scienceworld.wolfram.com/physics/KinematicViscosity.html
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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Its really strange that in #3 the balls in the water lose energy much
slower than the ones on the right side...
Lutz-Peter
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"Christoph Hormann" <chr### [at] gmxde> wrote in message
news:3CE29CC1.2B05A590@gmx.de...
> About that ball: don't forget the balls in that animation are fairly
> light, the surface tension effect is fairly strong in means of bodies
> sticking to the surface in such situations. Without it the balls are
> simply jumping back.
But it:
1) hits the bottom: suggesting heavy density
2) bounces right out: suggesting such low density that it gets a huge
boost from bouyancy.
When the looks don't match expectations of reality, change your parameters.
If you're not applying the drag instantaneously but rather frame by frame,
you lose the 'real' effect of the forces on your particle!
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"Greg M. Johnson" wrote:
>
> > About that ball: don't forget the balls in that animation are fairly
> > light, the surface tension effect is fairly strong in means of bodies
> > sticking to the surface in such situations. Without it the balls are
> > simply jumping back.
>
> But it:
> 1) hits the bottom: suggesting heavy density
No, just high kinetic energy.
>
> When the looks don't match expectations of reality, change your parameters.
The model should be changed in that case. Could be that stronger drag in
water is a convenient model for surface tension.
> If you're not applying the drag instantaneously but rather frame by frame,
> you lose the 'real' effect of the forces on your particle!
The drag is part of the movement equation just like all other forces.
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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Even cooler. :) Great work so far. Good luck with the surface tension
physics.
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Lutz-Peter Hooge wrote:
>
> Its really strange that in #3 the balls in the water lose energy much
> slower than the ones on the right side...
You have to take into account that due to buoyancy the influence of
gravity is more than compensated under water.
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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"Tony[B]" wrote:
>
> Even cooler. :) Great work so far.
Thanks!
Christoph
--
POV-Ray tutorials, IsoWood include,
TransSkin and more: http://www.tu-bs.de/~y0013390/
Last updated 05 May. 2002 _____./\/^>_*_<^\/\.______
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