bool OEMakeVoidVolume(const OEChem::OEMolBase &mol1,
                      const OEChem::OEMolBase &mol2,
                      OESystem::OEScalarGrid &grid,
                      float resolution,
                      float probeRadius = 1.4f)

Constructs a grid representing the void, or unoccupied, volume between a ligand (mol1) and a macromolecule (mol2) that can accommodate a spherical probe with radius less than probeRadius. The resolution of the grid is specified by resolution. The grid grid is resized to fit a 5 Angstrom envelope around mol1, and its values are set to 1.0 inside the void volume and 0.0 outside.