Design and Evaluation of Visual Feedback
for Virtual Grasp

 

Mores Prachyabrued, Faculty of ICT, Mahidol University

Christoph W. Borst, Center for Advanced Computer Studies, University of Louisiana at Lafayette

Abstract
We tuned and evaluated visual feedback for virtual grasps. Prior work on such feedback has been largely ad-hoc, without substantial guides for technique selection. Techniques included both standard and novel aspects (Figure 1).
 
 

Interpenetration Problem
 Penetration between real hands and virtual objects contributes to artifacts such as a sticking object when exaggerated finger motions are required for release, degrading performance and subjective experience. Users may reduce such problems using light touch. Visual cues may help a user understand and control this light touch.
 

Experiment Overview

Pilot study: 5 subjects tuned cue parameters per technique (e.g., transparency level, rate of color change) with a goal to “encourage light touch”.

Main study: 30 subjects picked up and dropped a ball repeatedly in the environment shown in Figure 2. A performance study measured finger penetration, release time, and error. Subjects later ranked techniques.

Main Results

Performance: The best-performing techniques are IH, ST, and 2H (Figure 3). They all directly reveal real hand configuration rather than using indirect representations of penetration.
Subjective Ranking: Color changes are most liked (OC and FC; Figure 4).


Recommendations: We recommend 2H because it ranks among the best performers and gives reasonable user experience. When subjective impression of the visuals is the overriding goal, OC and FC may be preferred.


Implications: An Updated Interaction Guideline
Standard 3D interaction guideline: Avoid penetrating visuals.


New guideline: Provide interpenetration cues. Moreover, for grasping:
• Subjectively, cues augmenting constrained visuals are promising.
• Performancewise, direct rendering of interpenetration can be better.
• Reasonable tradeoffs can be found.

 
 
Implications: An Updated Interaction Guideline
Standard 3D interaction guideline: Avoid penetrating visuals.
New guideline: Provide interpenetration cues. Moreover, for grasping:
• Subjectively, cues augmenting constrained visuals are promising.
• Performancewise, direct rendering of interpenetration can be better.
• Reasonable tradeoffs can be found