Target Expansion Lens

Abstract

To enhance pointing tasks, target expansion techniques allocate larger activation areas to targets. We distinguish two basic elements of a target expansion technique: the expansion algorithm and the visual aid on the effective expanded targets. We present a systematic analysis of the relevance of the visual aid provided by (1) existing target expansion techniques and (2) Expansion Lens. The latter is a new continuous technique for acquiring targets. Expansion Lens namely, uses a round area centered on the cursor: the lens. The users can see in the lens the target expanded area boundaries that the lens is hovering over. Expansion Lens serves as a magic lens revealing the underlying expansion algorithm. The design rationale of Expansion Lens is based on a systematic analysis of the relevance of the visual aid according to the three goal-oriented phases of a pointing task namely the starting, transfer and validation phases. Expansion Lens optimizes (1) the transfer phase by providing a simple-shaped visual aid centered on the cursor, and (2) the validation phase regarding error rates, by displaying the target expanded area boundaries. The results of our controlled experiment comparing Expansion Lens with four existing target expansion techniques show that Expansion Lens highlights a good trade-off for performance by being the less-error prone technique and the second fastest technique. The experimental data for each phase of the pointing task also confirm our design approach based on the relevance of the visual aid according to the phase of the pointing task.

Additive Voronoi Cursor: Dynamic Effective Areas Using Additively Weighted Voronoi Diagrams

“…Lastly, we could also observed that the method of IFC was significantly slower than the other four methods (p < 0.0005), and in general IFC had significantly higher error rate than the other four methods except for the cases of A = 768 and DRATIO = 1.5. IFC had a better performance than other tested area cursor techniques in their paper, this might be owing to IFC was the only technique that used implicit display style in their experiment, while in our paper, all tested area cursor techniques used implicit display style and the effect of different display styles on performance, as reported in [15,28], could be minimized. Since AVC, AVC+M.…”

“…Different from the standard Voronoi partition used in the ordinary Bubble area cursor, we hypothesized that the dynamic partition of the additively weighted Voronoi diagram (AWVD) in AVC would improve the efficiency of the correction cursor movement. Note that other literature [15,24] considered that the whole target-selection task involves extra phases besides the ballistic and correction phases, such as the searching phase before the starting of mouse movement, and the verifying phase after the correction movement and before the mouse clicking occurs. However, in this work, we do not focus on these extra phases, as the time spending on them would not significantly affect by area cursor techniques.…”

“…Moreover, displaying effective areas of all targets would overwhelm selectable targets and other UI elements, thus would not be appropriate for many applications. According to the findings of recent pieces of literature [15,28], an area cursor with dynamic target effective areas should hide the effective areas for better performance, as displaying the effective areas would distract users' attention and degrade target selection speed. Therefore, we adopted the implicit display style and hid the dynamic target effective areas, so that users will not aware of the update of the underlying Voronoi diagram when the cursor movement is switched from ballistic phase to correction phase.…”