  Interaction in virtual reality (VR) environments is essential to achieve a
pleasant and immersive experience. Most of the currently existing VR
applications, lack of robust object grasping and manipulation, which are the
cornerstone of interactive systems. Therefore, we propose a realistic, flexible
and robust grasping system that enables rich and real-time interactions in
virtual environments. It is visually realistic because it is completely
user-controlled, flexible because it can be used for different hand
configurations, and robust because it allows the manipulation of objects
regardless their geometry, i.e. hand is automatically fitted to the object
shape. In order to validate our proposal, an exhaustive qualitative and
quantitative performance analysis has been carried out. On the one hand,
qualitative evaluation was used in the assessment of the abstract aspects such
as: hand movement realism, interaction realism and motor control. On the other
hand, for the quantitative evaluation a novel error metric has been proposed to
visually analyze the performed grips. This metric is based on the computation
of the distance from the finger phalanges to the nearest contact point on the
object surface. These contact points can be used with different application
purposes, mainly in the field of robotics. As a conclusion, system evaluation
reports a similar performance between users with previous experience in virtual
reality applications and inexperienced users, referring to a steep learning
curve.
