Two-handed direct manipulation on the responsive workbench

We have built a systemthatallows usersto naturallymanipulatevirtual 3D models with both hands on the Responsive Workbench, a tabletop VR device. Our design is largely based upon Guiard's observations of how humans distribute work between the two hands in the real world. We show how to apply these principles for the workbench environment and describe many issues encountered during the design. We first develop a framework for two-handed interaction and then explore a variety of two-handed 3D tools and interactive techniques. Related issues include how constraints are implemented and controlled by the two hands and how transitions between one-handedand two-handed tasks occur seernlessly. Informal observations of the system in practice show that users can perform navigation and manipulation tasks easily and with little training using the two-handed environment. One of our interesting findings was that users often performed two-handed manipulations by combining two otherwise independent one-handed tools in a synergistic fashion. In these cases, we did not program two-handed behaviors explicitly into the system; instead they emerged naturally.