How do I control light direction when using normal map

Hi there,

I'm in the process of using the bumpmapping effect to apply a shadow on a terrain and do not really undertand how to control light direction.

In the enclosed example, I'm using a circular normal map to simulate a top view of a dome and would like to illuminate it from where the yellow dot is dragged on the scene. Apparently, it's not that easy. Any tip about that ?

And also, the illuminated part of the dome is white white and I'd like to have it a lighter shade of the material. Also any tip for shadowing ?

Thanks !

https://www.dropbox.com/s/zfm8bpslhcnp7 ... .capx?dl=0