What I generally do is determine the minimum and maximum extent of the
height_field using:
#declare Min = min_extent(Landscape).y;
#declare Max = max_extent(Landscape).y;
and use those values in the altitude parameter:
altitude <0.0, 0.2, 0.0> , Min , Max
You may then have to experiment further with your pigment_map{}
texture_map{} values of course to get what you want.
Hope this helps
Thomas
