I've been trying to figure this out for more than a day now and I think I've found a method. But I'd like to check it with other artists and see if I made any mistakes. Someone might also know a faster way, which would also be interesting.
Now, I've tried to use natural (sun) front lighting on my house in 2-point perspective. However, I don't know if this is the proper way to locate shadow points on a slanted surface (the roof, see image 1).
Image 2 contains my complete cast shadow rendering. Image 3 was done to practise back lighting.
Pointers and help would be greatly appreciated, thanks.