It evolved to enable the general mapping of atomic properties to the surface contour. Subsets of atoms, surfaces, properties, etc. may be defined and diplayed differentially.
Simple math is availble to manipulate the values of maps projected on the surface of macromolecules.
It is excellent for calculating and displaying surface properties , including internal cavity surfaces . The program also creates cpk, ball and stick, ribbons and tube models of macromolecules. The User Manual is available online or as hard copy in the core. There is also a Home Page for Grasp . Some local worked examples are available.