Revisiting peephole pointing: a study of target acquisition with a handheld projector

Peephole pointing is a promising interaction technique for large workspaces that contain more information than can be appropriately displayed on a single screen. In peephole pointing a window to the virtual workspace is moved in space to reveal additional content. In 2008, two different models for peephole pointing were discussed. Cao, Li and Balakrishnan proposed a two-component model, whereas Rohs and Oulasvirta investigated a similar model, but concluded that Fitts' law is sufficient for predicting peephole pointing performance. We present a user study performed with a handheld projector showing that Cao et al.'s model only outperforms Fitts' law in prediction accuracy when different peephole sizes are used and users have no prior knowledge of target location. Nevertheless, Fitts' law succeeds under the conditions most likely to occur. Additionally, we show that target overshooting is a key characteristic of peephole pointing and present the implementation of an orientation aware handheld projector that enables peephole interaction without instrumenting the environment.