Scheme - Conic edge specification

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Author

Conic edge specification

Kotya

2006-01-31, 4:09 am

Hello,

In TracePro (optical simulation program) I can create a conic curve by
specifying two points, tangents at these points and a conic constant
rho. For this constant it is said in help that it ranges from 0 to 1
exclusive with 0.5 for parabola. However the equation for this curve is
not provided.

Standard (at least for optics) conic surface specificaiton is
y(x) = cx^2 / (1+sqrt(1-(k+1)c^2 x^2) ),
where k ranges from 0 to minus infty, k=-1 for parabola, 0 for sphere.

So, to specify a conic in TracePro I need to connect k and rho. The
trivial equation rho = k/(k-1) didn't yield the correct result.

Can anybody help or suggest where I can find the conic equation used by
Scheme?

TIA!

Best regards,
Konstantin.

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