Étude de performance des interfaces humain-machine à base de métaphores visuelles pour les systèmes de réalité virtuelle

One of the factors that gave rise to the personal computer, the "PC", in the beginning of the 80's was the transition from a textual to a graphical interface, better adapted to the general public and easier to use. Given that fact, the present thesis aims to promote the emergence of a user interface that offers similar benefits for virtual reality systems. To attain this, we have developed a configurable and reusable VR test platform which forms the foundation allowing us to conduct experiments with human subjects, within a virtual environment where various conditions can be controlled. We used this platform for three experiments with human subjects that allowed gathering performance data related to the use of user interfaces within a virtual environment.

The first experiment aimed to study human performance variations related to the manipulation of floating menus in a three-dimensional space. We thus took a macroscopic approach, considering floating menus within their environment instead of focussing our attention on the menu content itself

Our results show that there is a reciprocal link between the number of degrees of liberty shared, between the reference frames of the user interface and the user's body, and the human performances. The performance grows with the number of shared degrees of liberty such that user interfaces which are attached to the user's body movements and position are preferable based on these results.

The second experiment aimed to study human performance variations related to user interface elements manipulations composing floating menus. We thus took a microscopic approach by considering local characteristics of these interface elements. The three characteristics that were studied are: the color changes, the use of the "cubic menu", a visual retroaction that we have created and finally, the projection of a hand shadow to provide more life-like realism to the eye of the user. We made these three characteristics vary during subject's manipulations to measure the manipulation time variations as well as the positional errors. Results show that there is a link between the visual retroaction used and the human performance related to user interface manipulations. We observed that the retroactions that aim to more closely recreate natural visual retroactions have shown to be less efficient. The color changes, followed closely by the cubic menu retroaction, have shown the best performance levels.

The third experiment aimed to study human performance variations in conditions where a longer task, requiring a higher degree of concentration, is proposed. During this experiment, we evaluated enhanced versions of the cubic menu and projected shadows retroactions that were used during the second experiment. The cubic menu version 2 uses a line and a circle to indicate the position and distance of the virtual pointer with regard to the floating menu. For the shadow version 2, the projected shadow opacity changes based on the distance variation of the virtual hand with regard to the floating menu. The results of this study have shown that the cubic menu version 2 has a positive impact on human performances.

The results of these experiments have allowed us to present a series of recommendations aimed at the creation of graphical interfaces that are adapted to the requirements specific to virtual environments encountered in virtual reality systems. The absence of standardisation is another important factor which has a negative impact on the evolution and the acceptance of the virtual reality technology among the public. The recommendations brought forward in this thesis are aimed to be generic and applicable to various virtual reality systems instead of targeting a specific application, effectively allowing the establishment of long-term design standards for virtual reality system user interfaces.

This research highlights that there exist a large range of research opportunities in the direction that we took. The results observed within this thesis show that there is a great potential for performance optimisation for this type of user interfaces which encourages us to pursue in this direction. (Abstract shortened by UMI.)