Proper integration of sensory cues facilitates 3D user interaction within virtual environments (VEs). Studies on multi-sensory integration of visual and haptic cues revealed that the integration follows maximum likelihood estimation (MLE). Little effort focuses however on integrating force and vibrotactile cues-two sub-categorical cues of the haptic modality. Hence, this paper presents an investigation on MLE's suitability for integrating these sub-categorical cues. Within a stereoscopic VE, human users performed a 3D interactive task of navigating a flying drone along a high-voltage transmission line in an inaccessible region and identifying defects on the line. The users had to identify defects via individual force or vibrotactile cues, and their combinations in colocated and dislocated settings. The co-located setting provided both cues on the right hand of the users; whereas the dislocated setting delivered the force and vibrotactile cues on the right hand and forearm of the users, respectively. Task performance of the users, such as completion time and accuracy, was assessed under each cue and setting. The presence of the vibrotactile cue promoted a better performance than the force cue alone. This was in agreement with the role of tactile cues in sensing surface properties, herein setting a baseline for using MLE. The task performance under the co-located setting indicated certain degrees of combining those under the individual cues. In contrast, the performance under the dislocated setting was alike that under the individual vibrotactile cue. These observations imply an inconclusiveness of MLE to integrate both cues in a co-located setting for 3D user interaction.

4 CONCLUSION AND FUTURE WORK This work revealed that the compass pattern yields better performance of navigation than the pushing pattern. This indicates a potential of using the compass pattern to facilitate navigation in VEs. Future work includes the refinement of the compass pattern for reducing cybersickness.

We propose an innovative method to navigate in a virtual environment by adapting the acceleration parameters to users in real time, in order to reduce cybersickness. Indeed, navigation parameters for most navigation interfaces are still determined by rate-control devices. Inappropriate parameter settings may lead to strong sickness, making the application unusable. Past research found that especially accelerations should not be set too high. Here, we define the accelerations as a function of a cybersickness indicator: the Electro-Dermal Activity (EDA). A pre-study was conducted to test the effectiveness of our approach and showed promising results where cybersickness tends to decrease with our adaptive navigation method.

This study proposes to investigate the effect of adding vibration feedback to a navigation task in virtual environment. Previous study used footstep vibrations and proprioceptive vibrations in order to decrease the cyber-sickness and increase the sense of presence. In this study, we experiment the same vibration modalities but with a new navigation method. The results show that proprioceptive vibrations do not impact the sense of presence neither the cyber-sickness while footstep vibrations increase sense of presence and decrease in a certain way cyber-sickness.

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