Hi Abdallah,
What you see in vectorview are representations of two gradient meters, in both planar directions, green and red and a magnitude mater in yellow. This is actually close to how a MEG sensor is in practice. I would suggest you to have a look at http://ilabs.washington.edu/what-magnetoencephalography-meg and then squid sensor.
The integration points are inside the perimeter of the sensors , though as far as I know not related to the drawing. They are there to sample the calculated magnetic field better than just using one point.
- The leadfield computes just 1 point, because eventually you will get one voltage out of the sensor. The integration points are to more or less "average" the field to get a better representation of what would happen in reality.
A more thorough explanation on this topic is given in : Computing the vector field B on the MEG sensors (forward problem)
Kind regards,
Steven