Wasn't it B. Gimeno who wrote:
>"Mike Williams" <nomail@nomail> wrote:
>> "Tim Attwood" <tim### [at] comcastnet> wrote:
>>
>> I suspect that B. Gimeno's image might possibly be getting the normals inside
>> out, at least over part of the surface.
>>
>> Here's a similar image, created with 900 triangles, that doesn't show 
>>the same
>> effect.
>
>Curious object, does it tried to be a torus shape?
>If so, let me see your code, the use of cross-reference between sine and cosine
>functions is wrong and is beyond my level of English and the google's automatic
>translator  ake myself understood, but I think I still remember how to get a
>decent torus with a nested-loop.

It's called a Bohemian Dome.

It's the shape that you get if you hold a circle flat and sweep it 
around a circle. For a torus, the diameter of the swept circle always 
points to the centre of the torus. For a Bohemian Dome the diameter of 
the circle always point in the same direction.

The surface intersects itself. The side that is the inside on one half 
is the outside on the other half. And POV even gets that right: it uses 
the interior_texture on the outside of one half.

It's generated by these parametric equations:
          x = A*cos(u)
          y = B*cos(v) + A*sin(u)
          z = C*sin(v)

Code to create it using a parametric isosurface (seriously slow) or 
using Ingo Janssen's "param.inc" to create a smooth mesh2 to approximate 
it (fast) can be found here:
          http://www.econym.demon.co.uk/isotut/param.htm

-- 
Mike Williams
Gentleman of Leisure

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