University of Padova

Super-Feet

SUPER-FEET
A WIRELESS HAND-FREE NAVIGATION SYSTEM FOR VIRTUAL ENVIRONMENTS.

(SUPERFEET WAS REALIZED BY THE LAB HUMAN, TECHNICAL UNIVERSITY OF VALENCIA. SPAIN. LAB HUMAN IS A HTLAB PARTNER LAB)

ABSTRACT

Super-Feet is a non invasive wireless navigation system controlled by natural movements, this device was designed on the basis of the physical locomotion metaphor. The user sitting on a chair can explore virtual environments by accomplishing movements that are similar to the ones he would make in the real world. The system is based on optical tracking so the hardware configuration does not require an excessive workload for the computer. According to previous studies [1, 2], the naturalness of movements seems to be related with higher presence in the virtual environment, so Super-Feet was designed and based on natural feet movements as similar as possible to real walking. Super-Feet detects the movements using a low cost infra-red commercial tracking system: Optitrack [3], which is connected to the computer via USB interface. The tracking device detects the movement of 2 markers that are positioned on the toe tips of the user’s feet (Fig.1.), so that when the user moves alternatively the toe tips leaving the heels on the floor, the system calculates the vertical velocity for each foot making him move straight forward in the VE.

The trackers The experimental setting
Fig.1. The trackers Fig.2. The experimental setting

If this movement is done quickly, the user will achieve greater velocities in the virtual environment. When the user moves the toe tip of the corresponding foot to the right or to the left he will consequently turn in that direction in the virtual environment. We performed an ergonomic evaluation of Super-Feet in order to understand the usability of the device in performing some basic movements in a digital environment. We decided to compare its functionalities with a joypad , and performed what is called a ‘comparative evaluation’ [4]. The movements selected for the tests were the following: a pre-defined path within a labyrinth-like environment; a double curve corridor; a rectilinear path along a corridor; a free walk in a two-floors indoor space in search of three specific items. All data were collected by a special software within a User-Interface Events (UIE) paradigm, based on the automatic gathering of the user’s operations on the interface together with their time of occurrence [5]. The results of the usability test show that there were no significant differences in performance indexes between Super-Feet and the Joypad, with the exception that Super-Feet seems more physically engaging and a more accurate device than the Joypad, which may be useful or not according to the task. Because of the physical requirements of the device if speed is requested by the task at the expenses of accuracy for long periods of time, then a joypad may perform better.
This allows us to conclude that Super-Feet can be used as a navigation system with similar results to the ones achieved with a commonly accepted navigation device as the joypad. The main advantages that have been obtained with this system when compared with other physical locomotion systems are:
a) It does not require the complexity of mechanical devices such as treadmills.
That makes it more portable and less invasive for the user.
b) It is based on feet movements, so hands are left free for other interactions inside the virtual environment.
c) It is not based on electromagnetical tracking devices, so it is less sensitive to noise and interferences.

Graph showing the time to accomplish the first task (left), route length (right) in the three experimental conditions
Fig. 3. Time to accomplish the first task (left), route length (right) in the three experimental conditions.

REFERENCES

[1] Slater, M., Usoh, M., Steed, A. Taking Steps: The Influence of a Walking Technique on Presence in Virtual Reality. ACM Transactions on Computer-Human Interaction, 2 (3),1995, 201-219.
[2] Usoh, M., Arthur, K. Whitton, M.C., Bastos, R., Steed, A., Slater, M., Brooks Jr., F.P. Walking > Walking-in-Place > Flying, in Virtual Environments. Proceedings of the 26th Annual Conference on Computer Graphics and Interactive Techniques, 1999, 359-364.
[3] NaturalPoint Homepage: http://www.naturalpoint.com
[4] Bowman, D. A and Gabbard, J. L. A survey of usability evaluation in Virtual Environments: Classification and Comparison of Methods. Presence, 11(4), 2002, 404-424.
[5] Hilbert, D. M and Redmiles, D. F. Extracting Usability Information from user Interface Events, ACM Computing Surveys, 32 (4), 2000, 384-421.

Daniel J. Kerrigan and Francesco Martino


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