Isovists / Visibility / heatmap

Hi, 

I am trying to develop a simple solution that evaluates which parts of a given surface (say facade) are visible from a number of sample points on another surface (say pedestrians on a ground plane) considering any obstacles that may exist. I have developed this for 1 sample point on the 'facade' and for several at once. For the several sample points get back a tree with several branches and all 'valid', ie. successful visual connections are in separate branches, but I can't seem to automatically count how many successful connections are associated with which sample point - which would be the basis to create some kind if hierarchy or heat-map.

Please see attached screenshots / definition.

Any comments or ideas how to solve this would be much appreciated!

Thanks,

Peter