In message <42eec1cf$1@news.povray.org>, Bob Hughes 
<omniverse@charter%net.?.invalid> writes
>Hey Alex, looks very believable (realistic) to me.

Thanks.

>Especially like your
>concept of using magnetic objects that add a sense of dynamics to these
>things.
>
>I don't suppose you've gone so far as to add motion to the pieces so it
>could animate? This series of similar yet different shapes made me think
>that might be plausible-- except possibly a little difficult.
>
They can be made to move. Depending on how many north or south poles are 
attached to each sphere, the spheres become magnetised themselves (not 
permanently). Smaller shapes can then be hung from another similarly 
magnetised sphere, which are then free to spin. It is possible to hang 
such shapes inside larger ones, but then the magnetic fields around the 
two shapes can interact unpredictably as the smaller shape spins.
Much easier to hold 1 rod in the air with a sphere stuck on one end, and 
hang the shape off that.

See http://www.geomagsa.com/cp_gioco.php?PageNum=3#su

Most regular shapes have some or all spheres with an odd number of rods 
attached, so it is impossible to balance the number of north and south 
poles to achieve no net magnetisation. So these shapes can have a 
complex magnetic field around them.
In fact the shape on the far right made a right mess of the picture on 
my monitor when I had it sat on my desk to study.

As for animating it in PovRay, It's possible. I'd have to give up the 
blurred reflections and area lights to reduce rendering times.
But I'm lazy, and I've got a couple of other things I'd like to try out 
as well as maybe some larger/more complex Geomag shapes.

I have thought about building a simple electronic circuit to switch some 
small electromagnets in sequence, in order to automatically spin such a 
shape. But I would have to re-wire it to change the sequence for 
different shapes.

>Sorry that I can't remember how you went about creating these. I saw an
>earlier picture or two, though.
>
I just calculate (almost by hand - I haven't written any clever programs 
or macros to do this) the co-ordinates of the balls. Then I have 2 
macros to place the parts. "placeball" takes a single co-ordinate, and 
puts a sphere there. "placerod" takes 2 co-ords and a texture index. It 
checks that the co-ords are the correct distance apart, and sticks a rod 
between them allowing space for where the balls go. The longitudinal 
rotation of the rod is random, and the texture index refers to one of 9 
rod textures (3 of which I made up). The silver-metallic one is a pig, 
it's clear plastic showing the central metal pin.
-- 
Alex

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