Shadow Diagrams - Overlay New on Existing

[Chris Loz]

I am trying to overlay the shadows of a new building over the shadows of the existing.
Is there a process for doing this efficiently? 
Attached images for reference of what I'm trying to achieve. 
Any solutions / pointers appreciated, thanks!

[Qualifa]

Hi @Chris Loz,

For a clean visualisation, I suggest you roughly recreate the layout of the buildings and show the result on the plan from above.

It is difficult for me to navigate these shadows because they are complex and you can see the height differences of the building.

If you are designing in a certain existing location, and I am sure you are, then you can use the maps to find out the heights of the neighbouring buildings, create the illusion that it is one, and make them simple to show and give a clear play of shadows.

They are quite simple and present a composition of parallelepipeds, I would do this.