Le 21/10/2011 07:46, Arun Kumar nous fit lire :
> Thanks again for your help.. It helped me a lot. I have created lens and front &
> side views which am exactly looking for. Now i need to calculate the focal
> length of the lens. How can i calculate the focal length.
> 
> To calculate focal length manually there is a formula
> 1/f = (n-1) {1/R1 - 1/R2}.
> 
> But how can i calculate it from the code.

The formula is wrong. (or rather, you forgot the interesting part)

it's

1/f = (n-1)( 1/R1 - 1/R2 + (n-1)d/(nR1R2))

(if I was to trust wikipedia :
http://en.wikipedia.org/wiki/Focal_length
)

R1 & R2 are the radius of the sphere.
d is the thickness of the intersection (at the line connecting the spheres)
n is the ior

Numeric application from previous code:
R1=6;
R2=6;
d=1;
n=1.5;
notice that 1/R1-1/R2 is null;

1/f = 0.5 ( 0.5*1/(1.5*6*6)) =
.00462962962962962962962962962962962962962962962962962962

or f= 216

Units (meter, foot, pov-unit) are irrelevant as they all ends up in the
same space (a linear length).

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