bookmark EDTSurf Implements an algorithm which uses Euclidean distance transform (EDT) to convert the target protein structure into a 3D gray-scale image, where depths of atoms in the protein can be conveniently and precisely derived from the minimum distance of the pixels to the surface of the protein. EDTSurf allows to construct triangulated surfaces for macromolecules. It generates three major macromolecular surfaces: van der Waals surface, solvent-accessible surface and molecular surface (solvent-excluded surface). EDTSurf also identifies cavities which are inside of macromolecules. Furthermore, EDTSurf has been extended to calculate atom depth and residue depth to solvent-accessible surface.