Dear Marco, thanks for the compliment and the solution, the last one works well.
It represent the magnetic field of a rectangular magnet, split in the three components, Bx, By and Bz.
The unique "selling feature" is the representation of a vectorfield as a function of the x,y,z position.
It is interesting for those who are involved in electro-magnetic fields, fluid/gas dynamics, etc.
I started more than one year ago with Mathematica and these pictures are unbeaten.
The next step is to add this to Wolfram Demonstrations.
Kind regards John Compter
