[Bf-committers] Solidify --> Thickness between two concentric shells

[Aaron J. Pung]

Greetings,

   I am trying to pre-determine the Thickness property of the Solidify
modifier required to completely fill the gap between two concentric,
spherical shells. I know the diameter of both shells ahead of time, the
shells will always be centered at (0,0,0). I would like to keep Offset =
-1.0.

   Using a number of examples, I have tried to back out a mathematical
relationship / equation, based on the difference in the diameter of the
shells.  But this falls apart when the shells diameters change, but the
difference between the shell diameters remains the same.

*Example: *
    If i have a hemisphere of diameter1 = 8m, and a smaller, concentric
shell with diameter1 = 2m (difference = 6m), then a Thickness value of
0.7485 will fill the gap between these two hemispherical shells.
   However, if I use 2 shells that are diam1 = 100m, and diam2 = 94m
(difference = 6m), then a Thickness value of 0.05975 fills in the gap
between the concentric shells.

How can I pre-determine what this thickness needs to be for any case of 2
concentric shells?

Thank you.
Aaron