A study of the performance of steering tasks under spatial transformation of input.

ABSTRACTTypical direct manipulation tasks often suffer from an inherent indirection between the virtual objects that form the computer interface and the input devices through which the user interacts to manipulate these objects. This paper studies the effect of spatial indirection on the performance of interaction. For continuous input devices, spatial transformation can be decomposed into translation, rotation, and scale. Translation alone simply shifts a movement from the device space to a different position in the virtual space, preserving the direction and size of that motion. Rotation changes the direction, while scale modifies the size. This study found evidence that rotation and scale are significant factors in interaction performance. We propose a model based on these factors that can be employed to predict the time required for a task of tracing and staying inside a non-linear shape. Contrary to our initial hypothesis, moderate translation changes did not register significant variations in the required time. The results of this study are also applicable to the placement and ergonomics of physical input devices.