I started a new project and I got this problem with my shadows :
As you can see, the shadows on the ground have rounded corners, my lightmap seems to be ok but maybe I’m doing it wrong (you can see it by following the link bellow)
Lightmap : http://imagizer.imageshack.us/a/img908/6490/d8WmVz.jpg
I set it to 1024 and the building quality is set to production mode.
Hope we’ll find the solution off my problem
Thanks to everyone !