DEM to volumetiric

converts a Digital Elevation Model (or 2.5D data) to a volumetric raster (or true 3D data)

In a DEM height information is strored as h(x,y). This scripts converts h(x,y) to I(x,y,z) based on

(a) if z < h(x,y) then I(x,y,z) = 1
(b I(x,y,z) = 0 otherwise.