Object manipulation in cluttered virtual environments (VEs)
brings additional challenges to the design of interaction
algorithms, when compared with open virtual spaces. As the
complexity of the algorithms increases so does the flexibility with
which users can interact, but this is at the expense of much
greater difficulties in implementation for developers. Three rules
that increase the realism and flexibility of interaction are outlined:
collision response, order of control, and physical compatibility.
The implementation of each is described, highlighting the
substantial increase in algorithm complexity that arises. Data are
reported from an experiment in which participants manipulated a
bulky virtual object through parts of a virtual building (the piano
movers’ problem). These data illustrate the benefits to users that
accrue from implementing flexible rules of interaction
