[Sussex] Help! Equation for a surface wantted.

[Steve Dobson]

Mark

On Fri, Oct 21, 2005 at 03:56:20PM +0100, Mark Harrison (Groups) wrote:
> On Thu, 2005-10-20 at 20:10 +0100, Steve Dobson wrote:
> > 
> > The surface I want is very similar to a torus, but the radius of
> > the circle changes linearly between two values.
> 
> Too many circles to work out what you're after:

That maybe the case - but I have seen it, I just don't know who to 
generated it.

> - Possibility 1, you are looking for something like a circle extruded
> round an ellipse. (Think a normal doughnut that you are pulling apart
> from opposite "corners".)

That's called a torus - that I know how to produce.  I gave the equation
for this the grandparent post.

> - Possibility 2, you are looking for something like a doughnut, but at
> some points of the doughnut the dough is thicker than others, however,
> cutting through the dough at any point always gives a circle.

If the cut is being made perpendicular to the axis of rotation then this
is what I want.  If you cut my odd shaped doughnut in half then the to
circle cross sections, while perfectly circular, would nit necessarily
have the same radius.  I only need to specify one maximum and one minimum 
radius for the cross section circles - the others can be a linear
progression from the max to the min.

> - Possibility 3, you are looking for something like a doughnut, but
> instead of the dough bit being a circle, the dough bit is an ellipse, so
> you are effectively extruding an ellipse round a circle.

No, see above.

I hope this allows you to determine the surface I need.

Steve

-- 
Arithmetic is being able to count up to twenty without taking off your shoes.
		-- Mickey Mouse
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