Effects of Control-Display Mapping and Spatially Dependent Gain on Supported Free-Hand Gesture Pointing Performance

Abstract

While gesture controls will be important as future computing input modalities, they are limited by reduced performance and increase ergonomic risk. Performance of pointing in free-hand gestural controls is affected by control-display (CD) parameters such as gain and mapping, but specific CD function parameters that yield optimal performance are unclear. This paper describes an experiment that examines the effect of altering CD gain in different movement directions (‘spatially dependent gain’, SDG) for different CD mappings on their performance in armrest-supported pointing tasks. Thirteen participants were given a series of circular Fitts’ tasks with different fixed CD gain and mapping settings. The SDG was used to warp the Fitts’ circle in the participants’ physical motor-space in order to take advantage of inherent motor performance differences. Additionally, the placement of the movement controller was also studied. The results show that mapping is the most significant factor; vertical mapping produced throughput results that were approximately 0.5 bits/s greater on average than the other mappings. Vertical mapping is also where CD gain shows the most effect. Lower gain settings produce results that are 0.14 bits/s faster than higher gain when the user is in vertical mapping. No significant differences were found in pointing performance between SDG conditions. These preliminary results suggest that participants adapt easily to motor-space warping and that further study of non-fixed gain functions (e.g. pointer acceleration functions) is necessary in order to maximize free-hand performance.