Digital elevation model support

The DEMExperiment class extends the capabilities of the AtmosphereExperiment class with digital elevation model support. This class supports all the parameters allowed by AtmosphereExperiment, except for the surface parameter, which accepts a DEMSurface instance. It should be noted that any experiment performed with this class is 3D.

A DEMSurface features two components:

• a main terrain shape of a finite horizontal extent, consisting of a triangulated mesh;

• a background shape, which defines the surface outside of the terrain’s extent.

Background control is limited to setting the associated reflection model. The terrain shape and

The DEM can be defined in several ways and it can be used with any surface reflection model. The DEM dataset is converted into a 3D shape and integrated in a background 1D experiment. Eradiate makes sure that the 3D model derived from the DEM dataset is integrated in the background surface in a watertight fashion so as to avoid any energy leakage that would occur if rays could escape under the terrain model.

The DEM geometry is defined using one of the mesh classes (FileMeshShape if loaded from disk, or BufferMeshShape if initialized from an in-memory buffer). The dem_from_mesh() helper facilitates the operation of building a triangulated mesh in memory from a NetCDF dataset.