Achill Schuermann wrote:
> 
> Mathematically, the (vector) sum A+B of two sets A and B is defined as
> the set of all points x=a+b with a in A and b in B.
> A+B = { x : x=a+b, a in A and b in B }.

I have no idea what you are talking about but we are not dealing with sets
of points but with surfaces.  Your definition of a vector sum does not
seem to be applicable for surfaces.  

> A "simple" example is the sum of two convex polyhedra (cube,
> tetrahedron, octahedron, etc.) which is again a polyhedron.

That's not an example.  

Let's say we have a unit cube between <0,0,0> and <1,1,1> and a sphere at
<0,0,0> with radius 1.  What is the 'vector sum' of these objects?

Christoph

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