Section: New Results

Impact of form factors and input conditions on absolute indirect-touch pointing tasks

Absolute indirect interaction maps the absolute position of a device's end-effector to the absolute position of a remote on screen object. Despite its long-time use with graphics tablets and growing use in research prototypes, little is known on the influence of form factors and input conditions on pointing performance with such a mapping. The input and display can have different sizes and aspect ratios, for example. The on-screen targets can vary in size. Users can look solely at the display or at the input device as well. They can also hold the input device in certain cases, or let it rest on a table. We ran two experiments designed to investigate the influence of all these factors on absolute indirect-touch pointing performance [20] , [11] .

The first experiment focused on input device size and input conditions and revealed that users get higher performance when they can look at the input surface (even if nothing is displayed on it). In addition we found that the smallest target size users can acquire in motor space is not constant across different input dimensions but degrades as the input size increases. The second experiment focused on scale effects and aspect ratio and revealed users' performance is not affected by scale but that aspect ratio matters: similar input and output aspect ratios lead to better performance. This findings led us to list four main recommendations for the design of touch input surfaces with applications supporting absolute direct interaction.