Analysis of Medium Wrap Freehand Virtual Object Grasping in Exocentric Mixed Reality

Abstract

This article presents an analysis into the accuracy and problems of freehand grasping in exocentric Mixed Reality (MR). We report on two experiments (1710 grasps) which quantify the influence different virtual object shape, size and position has on the most common physical grasp, a medium wrap. We propose two methods for grasp measurement, namely, the Grasp Aperture (GAp) and Grasp Displacement (GDisp). Controlled laboratory conditions are used where 30 right-handed participants attempt to recreate a medium wrap grasp. We present a comprehensive statistical analysis of the results giving pairwise comparisons of all conditions under test. The results illustrate that user Grasp Aperture varies less than expected in comparison to the variation of virtual object size, with common aperture sizes found. Regarding the position of the virtual object, depth estimation is often mismatched due to under judgement of the z position and x, y displacement has common patterns. Results from this work can be applied to aid in the development of freehand grasping and considered as the first study into accuracy of freehand grasping in MR, provide a starting point for future interaction design.

Freehand Grasping: An Analysis of Grasping for Docking Tasks in Virtual Reality

“…We then compared these categories across grasping metrics for each experiment condition and show that there are significant differences between object categories for grasp metrics, showing that virtual object shape influences grasping approach in VR. A similar result was observed in Mixed Reality, namely that object shape and size influenced the grasping approach [2]. Further, we compared experiment conditions for each object category and found that there were no differences between conditions for grasp metrics.…”

“…Recent VR systems use the hand, the most powerful tool through which we interact with the surrounding world, as the main interaction tool [1]. However, when creating bare hand interactive systems, aiming to provide seamless and intuitive interactions, researchers have focused on a natural approach known as grasping [2].…”

“…However, this knowledge cannot be directly applied to grasping virtual objects, as it has been identified that users interact with virtual objects differently than they interact with real objects [51]. Therefore, virtual grasping has been explored as a technical challenge [10,11], with the aim of enabling users to manipulate virtual objects as if they were real [2,13]. However, current approaches predominantly rely on computed grasps, not taking into account humans' grasping actions [41].…”

“…Grasping is the primary form of manual interaction between humans and the physical world [2] and is defined as every static posture at which an object can be held securely with a single hand [33]. While grasping real objects has been highly explored before [61], grasping virtual objects in a natural manner is still a challenge [60].…”

Head Mounted Display Interaction Evaluation: Manipulating Virtual Objects in Augmented Reality

“…Researchers are currently evolving gesture interactions into physical interactions, thus, completely mimicking the interaction performed in the real world, into AR environments [46,49]. The work of Al-Kalbani et al [4] and [5] have sought to understand the complex nature of the human grasp for freehand interaction and defined the problems associated with grasping objects in AR, Ciodota et al [15] evaluated the application of grasps in AR and also Swan et al [51] evaluated the problems associated with representing and reaching the true located space of augmented objects.…”