An interactive molecular graphics system with a satellite terminal closely coupled to its host

GRIP is an experimental interactive computer graphics system being developed at the University of North Carolina for displaying, evaluating and manipulating models of complex molecular structures. The system displays a molecule as a network of line segments representing the locations and orientations of the atoms and valence bonds in the structure. It can also display electron-density data (obtained by crystallographic methods) as a three-dimensional contour map. The user can command the system to measure selected distances and angles in the model and to calculate functions of the molecular conformation such as its internal potential energy. He can also move the atoms about in the model space, either singly or in groups as specified by a vector or to minimize certain functions of the conformation. The user commands the system to execute one of these operations by selecting a light button. The parameters for such a command are specified by other light buttons, by selecting lines representing bonds in the molecular display, and by keyboard entry of scalar values. In addition to these discrete commands, the user has continuous, real-time manual control of the direction from which he views the model and of the position and orientation of a selected part of the model.