In above example. Please also include the 1/3rd area of the light in between three spheres shadow to be area restricted by one sphere.
Then divide the whole area of outer sphere by the sum of 1 shadow and the 1/3rd light falling on the outer most sphere
In above example. Please also include the 1/3rd area of the light in between three spheres shadow to be area restricted by one sphere.
Then divide the whole area of outer sphere by the sum of 1 shadow and the 1/3rd light falling on the outer most sphere