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Re: [ATM] Conic height



Richard Schwartz wrote:
> If you know the direction cosines for the ray, it is pretty easy to transfer
> from the tangent plane to the sphere.   For the conic, you must do some
> iteration, but it does converge very quickly.

Actually, no iteration is needed in that case.  If the conic is
given by:

	y^2 = 2*R*z - (SC+1)*z^2

and the original height and direction are given by y0 and t0 (where t0
is the tangent of the angle that the direction makes with the z axis),
then:

       (t^2 + (SC+1))*z^2 - 2*(R - y0*t)*z + y0^2 = 0

easily soluable [up to the ambiguity, but then that is also soluble
with a little thought].

But that was not the case under investigation.

-- 

Rick S.

http://users.rcn.com/rflrs

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