Displaying a picture on terrain under moving actor

Hi, I'm using Unity terrain to create world map and an actor who walks on the ground. I want to display a picture (png with transparency) under it so that it adapts to the terrain, i.e. if there is a hole, it takes its shape (projection effect).

I tried to use projector from Standard Assets, the system is almost perfect but it provides just 2 handcoded shaders which are lightening or darkening the displayed pic.

Is there any solution how to get an original brightness of a pic casted under my actor?