In article <3b15ecda@news.povray.org>,
 "Gail Shaw" <gsh### [at] monotixcoza> wrote:

> Now do a black hole <grin>

Those *are* black holes...he's using the equations for a point source, a 
singularity. Spherical masses with a radius larger than 0 don't have 
this falloff...unfortunately, I don't know the equation for the 
gravitational force of a spherical body.

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

<><

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"Rune" <run### [at] mobilixnetdk> wrote in message
news:3b16a26a@news.povray.org...
> "Bill DeWitt" wrote:
> >     But the problem with the formula I am using is
> > that it goes vertical too far from the center. The
> > larger the mass, the wider the area of nearly
> > vertical descent.
>
> scale <1, 0.1, 1>

    That's cheating. I want something that really works.

> I also think it would look nice if the planets etc. were placed down in
the
> holes instead of hovering over them. That way I think it would look more
> like the holes are a direct effect of the objects.

    I tried that and it did look better to me... but then the planets are
not on one plane. With two objects it was not too bad, but as soon as I
added a third it was obviously wrong. It looked like the earth was orbiting
the top quarter of the sun...

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On Thu, 31 May 2001 15:00:06 -0400, Chris Huff wrote:
>In article <3b15ecda@news.povray.org>,
> "Gail Shaw" <gsh### [at] monotixcoza> wrote:
>
>> Now do a black hole <grin>
>
>Those *are* black holes...he's using the equations for a point source, a 
>singularity. Spherical masses with a radius larger than 0 don't have 
>this falloff...unfortunately, I don't know the equation for the 
>gravitational force of a spherical body.

It's the integral of the one for a point source over the volume of the sphere,
of course.  Not that that's useful. :)

-- 
#macro R(L P)sphere{L F}cylinder{L P F}#end#macro P(V)merge{R(z+a z)R(-z a-z)R(a
-z-z-z a+z)torus{1F clipped_by{plane{a 0}}}translate V}#end#macro Z(a F T)merge{
P(z+a)P(z-a)R(-z-z-x a)pigment{rgbt 1}hollow interior{media{emission T}}finish{
reflection.1}}#end Z(-x-x.2y)Z(-x-x.4x)camera{location z*-10rotate x*90}

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"Chris Huff" <chr### [at] maccom> wrote in message
news:chr### [at] povrayorg...
>
> Those *are* black holes...he's using the equations for a point source, a
> singularity. Spherical masses with a radius larger than 0 don't have
> this falloff...unfortunately, I don't know the equation for the
> gravitational force of a spherical body.

Maybe these web pages have the answer, I sure don't.

http://www.ac.wwu.edu/~vawter/PhysicsNet/Topics/Gravity/AccOfGravity.html

Have a look at the gravitational force link there too.

Bob H.

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"Bill DeWitt" wrote:
> "Rune" wrote:
> > scale <1, 0.1, 1>
>
>     That's cheating. I want something that really works.

If I have understood correctly the surface is a visualization only. How can
there be a fixed relationship between the mass and the effect it has on the
surface? May I ask what distance values and what mass values are the current
model based on? Imagine what would happen if you used another base unit for
distances but still used the same base unit for masses. Then you'd change
the sizes of your planets, and thus the holes would become larger or smaller
horizontally but keep the same depth. Or something like that...

> > I also think it would look nice if the planets etc.
> > were placed down in the holes instead of hovering over
> > them. That way I think it would look more like the
> > holes are a direct effect of the objects.
>
>     I tried that and it did look better to me... but then the planets are
> not on one plane. With two objects it was not too bad, but as soon as I
> added a third it was obviously wrong. It looked like the earth was
orbiting
> the top quarter of the sun...

If you say so...

Rune
--
3D images and anims, include files, tutorials and more:
Rune's World:    http://rsj.mobilixnet.dk (updated May 10)
POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk

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