Peter Popov wrote:
> 
> Greetings all.
> 
> Suppose I have a sphere that is electrostatically charged. The
> intensity of its field at any point in space is proportional to the
> reciprocal squared distance, and the vector points away from the
> sphere. For a plane, it's easy. I think I can manage torii, cylinders,
> and cones. Even non-smoothed meshes.
> 
> How about a smoothed mesh? OK, I have all the vertices and
> corresponding normals stored in two arrays, but then what? How should
> I proceed to calculate the field vector and intensity at an arbitrary
> point in space?
> 
> And yeah, I am talking about POV script here, not C :)
> 
> Thanks in advance for any help.
> 
> Peter Popov
> ICQ: 15002700


Uhhhmmmm.......

Peter, are you talking about a meshed representation of a squere? Then
don't bother about the mesh. Or are you trying to compute the electric
field for an arbitrary body given by a mesh? Then don't bother about the
sphere.

The (infinite) plane has a completely different electric field than the
point load. E.g. it is constant. Just image two plates of a condensator,
the field in the middle (just far enough from the egdes) is constant.

I guess, you wan't to do the latter (general body).
The only way I can think of for doing the thing you want is via the
Green's function for electrostatics. This is in principal just the thing
you did above for each and every microscopic charge. Thus, this get's an
integral in the end. And I would use the unsmoothed mesh for that.
The electric field is given by
E = (4\pi\epsilon_0)^{-1} \int \rho (r-r_0)/|r-r_0|^3 dV
This is an integral over the density of the electric charge times the
radial term over the complete space. You than take the distribution of
the charge as a 2D density on the surface of your body,
E = \sum{over all triangles} \int{triangle} \rho_{2d} ()/||^3 dA
which is a sum over integrals over areas.
This cannot be done analytically, at least maple did'nt. So you go for
gaussion quadrature formulae.

These and further explanations on request. I guess you're fate is just
vanishing. And I don't really know how much explanation of physics
and/or algorithms you need

Dipl. Phys. Axel Hecht.

Yes, I have been studying physics. And now I am in scientific computing.
Excuse the long an tough answer.

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