Am 17.07.2012 11:49, schrieb peter puzzelaar:

> I am getting stuck on constructing a piece of an assembly.
>
> This piece I want is a sector of a torus-ish element.
> So let's describe this torus-ish thing...
>
> Scale a normal torus in the y-direction:
>    #declare myTorus= torus {24, 0.4 sturm on scale <1, 2, 1>}
>
> Now I want to tilt the complete (scaled) torus inward (AND preserving the 2:1
> ratio of the cross section of the tube)
>
> I tried several things, like shearing with matrix  (which does indeed tilt the
> torus: if applied on quarter of torus, and then connect 4 of these quarters
> again
> to get full torus again. You have a nice inward tilted torus).
> However - no matter what i tried - it leads to a very flat torus - so no longer
> preserving the 2:1 ratio of the cross section of the tube).
>
> I would be happy for any advice on how to make a torus which has 2:1 ratio of
> its tube preserved and can be tilted any degrees (0 to 90) inward/outward.

You won't get far with the torus primitive, but here are a few possible 
approaches:

* Use an isosurface; you'll need to figure out a function that will 
yield a rotated ellipsis, and combine that with another function to 
generate a surface of revolution.

* Approximate the shape using a sor or lathe object.

* Approximate the shape using a mesh.

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