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

Lukas Tönne lukas.toenne at gmail.com
Fri Sep 11 09:52:18 CEST 2015

```First off, this kind of question could better be answered on
http://blender.stackexchange.com/

I'm quite sure the thickness parameter gives a direct offset from the
surface, i.e. a perfect sphere with radius R and solidify thickness X
creates a sphere with radius (R+X). This matches the first observation,
where dR=3 => thickness = 1.5 / 2 = 0.75 ~= 0.7485. The reason you don't
see these values in the second case is probably because the object is
scaled by 100/8 = 12.5 => thickness = 0.75 / 12.5 = 0.06

On Fri, Sep 11, 2015 at 4:59 AM, Aaron J. Pung <aaron.pung at gmail.com> wrote:

> 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
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```