Location To Weight map

[Pancho]

P.S.: I understand why it get lit in the shadow area, but how do I approach this thing to avoid it???

[Chris_TC]

Raycast from every point on your mesh towards the light (with the Normal offset of course). If you hit the mesh, this point is in shadow. If you don't hit the mesh, the point is lit.

[EricTRocks]

Using Chris_TC's logic here is a screen grab for a working ICE Tree setting the weight map value as I believe you need.