This thesis introduces BodyScape, a body-centric framework that accounts for how users coordinate their movements within and across their own limbs in order to interact with a wide range of devices, across multiple surfaces. It introduces a graphical notation that describes interaction techniques in terms of (1) motor assemblies responsible for performing a control task (input motor assembly) or bringing the body into a position to visually perceive output (output motor assembly), and (2) the movement coordination of motor assemblies, relative to the body or fixed in the world, with respect to the interactive environment. This thesis applies BodyScape to 1) investigate the role of support in a set of novel bimanual interaction techniques for hand-held devices, 2) analyze the competing effect across multiple input movements, and 3) compare twelve pan-and-zoom techniques on a wall-sized display to determine the roles of guidance and interference on performance. Using BodyScape to characterize interaction clarifies the role of device support on the user's balance and subsequent comfort and performance. It allows designers to identify situations in which multiple body movements interfere with each other, with a corresponding decrease in performance. Finally, it highlights the trade-offs among different combinations of techniques, enabling the analysis and generation of a variety of multi-surface interaction techniques. I argue that including a body-centric perspective when defining interaction techniques is essential for addressing the combinatorial explosion of interactive devices in multi-surface environments.
