Sun is precious in cities - tall buildings overshadow their near neighbours - even sometimes their distant neighbours. This is why in almost every city there are laws governing solar access.
A customer recently asked us to create a solar tool for his jurisdiction (in Israel!)
My design experience is in Australia, but luckily the maths of solar access is the same around the world. So is the fundamental question approving authorities ask: what is overshadowed when?
This is the app we made:
Note, that for this early stage analysis we do it on a flat surface: it does not account for slope in topography.
This matters less than people think. The angles of the shadows remain the same no matter the topography, the thing that changes is their length. You can quickly make mental adjustments for this as as you design.
This is an important in early stage design: you need to do analysis, but it should be simple analysis. Labouring it slows the design process down to much. Roughly right is better than precisely late (and probably never done).
Giraffe offers a different view of the same project with 3D topography which you can use to convince yourself of this, and do more detailed point analysis.
The app quickly answers the question of what is overshadowed when. It also gives an idea of total sunlit hours on the surfaces of the design geometry. This is a very useful indicator for assessing which windows get too much, or too little sun, giving ideas and areas of where to put solar panels and informing landscape planting and shading design.
*This app is available now for $10/month, reach out in the chat to get it!