GIST: Gesture-free Interaction by the Status of Thumb; an interaction technique for Virtual Environments

User interface has special importance in immersive virtual environments. Interactions based on the simple and conceivable gestures of a hand may enhance immersivity of a Virtual Environment (VE).  However, due to the structural issues like small size and complex shape of human hand, recognition of hand gestures are more challenging. This work introduces a novel interaction technique to perform the basic interaction tasks by the simple movement of hand instead of distinct gestures. With an ordinary camera, the fist posture of hand is segmented out from the image stream using the optimal segmentation model. Like pressing a button with a thumb, the status of thumb is traced for the activation or deactivation of the interactions.  After the activation of interaction, the trajectory of hand is followed to manipulate a virtual object about an arbitrary axis. Without training and comparison of gestures, the basic interactions required in a VE are performed by the perceptive movement of a hand. By incorporating image processing in the realm of VE, the technique is implemented in a case-study project; FIRST (Feasible Interaction by Recognizing the Status of Thumb). A group of 12 users evaluated the system in a moderate lighting condition. Outcomes of the evaluation revealed that the technique is suitable for Virtual Reality (VR) applications.