bool OEMakeCavitySurfaces(const OEChem::OEMolBase &mol, OESurface &surf,
                          float resolution=0.5f, float probeRadius = 1.4f)

Create a surface, surf, from the macromolecule, mol, representing where solvent can be occluded inside the molecule. Therefore, this will not give cavities contiguous with the outside of the molecule. The resolution is the grid spacing to use during surface construction. The probeRadius is the size of the solvent probe to use, in Angstroms.