The user has to be given a realistic sensation that he or she is actually touching and manipulating physical objects. Motions made by a user modify the models specifying the virtual world appropriately. Stick-slip friction is simulated according to a modification of Karnopp's method. Assembly physics . As the user sets virtual objects in an assembly into motion, appropriate inertial and contact forces have to be generated and the positional evolution predicted.
Coordinate systems have to be established to allow flexible redefinition of assemblies and chains.
Real-time architecture . The computing environment on the Motorola 604e and 68040 microprocessors comprises VxWorks and ControlShell. Finite state machines and controller diagrams have been developed using a library of ControlShell components . We are currently working at replacing the ethernet connection with Myrinet, as part of the Department's NSF Infrastructure Award. The result will be to remove the communication latency between workstations and micros, allowing workstations to play a more direct real-time role.