How to do 3d building model visibility analysis

[HoiWaiCheung]

I have created a 3D model in ArcScene. (Giving Z-coordinate to polygon to create 3D shape)

 

I want to do a 3D analysis to the model to see how many of the building surface area have a clear view on the park nearby. But I realized in the TOOL section, all visibility analysis method (the line of sight ) could only do a single observer point to target (point, line, area).

 

Is there anyway to analysis the model base on the surface area as observer instead of point. Or, could I set up a something to tell the analysis to generate multiple observer point on every building surface (Let say every 2 meter width and height, generate a observer point), then procced the 3D visibility analysis for all building automatically?