A ellipse has the formula (in two dimensions) x^2/a^2 + y^2/b^2 = c^2
where the major axis is a or b depending on which is larger.  In an
ellipse, any ray drawn from a foci and bounced off a wall will terminate
in the other foci.  There are actually two foci instead of one radius. 
Anyhow...question for you... where is the center of the torus you use in
relation to the boxes?  I ask this, because from the image, I think
rotation of the cylinder is required.  However if you send me some
source I could be more helpful... (feel free to email it to me)

Steve



Philippe Debar wrote:
> 
> Hi Stephen (and everybody else reading this)
> 
> I am sorry, but I do not understand your answer. Well,
> I think I understand it, but I do not see how it can solve
> my problem.
> 
> I don't see the difference between
> (a) working with semi-axis ('radii') of r and R
> and
> (b) semi-axis of R and L*R
> 
> Isn't a scaled circle (cylinder) an ellipse ?
> circle at origin:
>   x=R*cos(theta)
>   y=R*sin(theta)
> 
> scale <1,L,*> =>
>   x=1*R*cos(theta)=R*cos(theta)
>   y=L*R*cos(theta)
> 
> translate <x0,y0,*>
>   x=x0+R*cos(theta)
>   y=y0+L*R*cos(theta)
> 
> - this is an ellipse
> 
> Is this wrong?
> 
> (See also my next post which explain my
> problem further)
> 
> Thanks
> 
> Philippe

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