Selection is one of the fundamental tasks in virtual reality applications and the initial task for most common user's interactions in a virtual environment. In this thesis we analyze major factors influencing selection performance, and propose new techniques for facilitating selection in 3D space. Considering the frequency of selection tasks in a typical virtual reality workflow, improving selection tasks often results in significant gains in the overall user performance.
A 3D selection task requires the user to gesture in 3D space, e.g. grabbing an object or pointing to something. The success or failure of the task depends mainly on the interaction technique, the dexterity of the user, and the spatial perception of the virtual environment. Since the dexterity of the user can be improved by training, we focus on how to take advantage of existing human control models to minimize the effort required to select an object, and how to enhance the user's spatial perception of the virtual environment to facilitate selection and referral tasks. We have proposed several selection techniques based on Fitts' Law and we have studied how visual feedback can be used to overcome spatial perception limitations in virtual environments. The techniques proposed are not only oriented to achieve performance gains as we also account for user's preferences. During the development of this thesis we have conducted a number of user studies, both to validate our theoretical analyses, and to compare the proposed selection techniques to existing ones.
Although the major contributions of this thesis refer to the selection of 3D objects, we also provide new techniques for facilitating the interaction with 2D graphical user interfaces embedded in 3D space. We also explore selection tasks in collaborative virtual environments. In CVEs pointing tasks often change their purpose and turn into referring tasks. Referential awareness can be compromised in complex environments, because a user can point to a feature in the environment which might be occluded for the other users. We have analyzed how improvements on referential awareness increase the information exchange among users without violating social protocols in formal presentations.