[Insight-users] How to create/draw a sphere surface image mask with 26|6 connectivity?

[lynx.abraxas at freenet.de]

Hello!


I  need  a  3D  mask of a sphere suface once with 26 connectivity, once with 6
connectivity and once with aliasing (as a weighting mask).
The mask should be a cube of size NxNxN where N is odd (corresponding to  some
definit  physsical  size) such that the centre pixel of the cube should be the
centre of the sphere with a physical radius of 1.

I was thinking of doing it with a for loop over all indices of the mask volume
but  there  I don't know how to realize the none aliased cases. The aliasing I
think could be done by assigning a grey value corresponding  to  the  distance
from  the  actual  radius-point  to  the  nearest voxel-centre. The grey value
should be down at zero for a distance bigger than one voxel.

Looking at the docs I found the ellipsoid spacial object but nothing about how
to  "render"  that  into a 3D image and again no clue how to differentiate the
three "rendering cases".

How could that be done with ITK or VTK?
Is there a way to implement also a surface thickness bigger than 1 voxel?

Many thanks for any help or hints.
Lynx