techniques, improving device transparency via path specific orientation, and by implementing extrasensory stimuli to engage the user. The above concepts are.
Developing Immersive Virtual Worlds through Realistic Contact Rendering and Improved Transparency Arash Mohtat, Colin Gallacher, and Jozsef Kovecses Department of Mechanical Engineering and Centre for Intelligent Machines McGill University, Montreal, QC Abstract. A haptic interface enables users to interact with virtual environments through the sensation of touch. In a force feedback device, the forces that arise from this interaction are relayed to the human user. These forces must accurately emulate a real interaction. Many different factors can influence the perceived haptic experience, and make realistic rendering a challenge. The work presented here realizes an immersive virtual world through combining rigid body rendering techniques, improving device transparency via path specific orientation, and by implementing extrasensory stimuli to engage the user. The above concepts are demonstrated by way of a virtual billiard game. This demo employs the W5D device by Entact Robotics, S-functions using the W5D API, Simulink Real-Time Workshop and the VRML Blockset.
Realistic Contact Rendering: A critical component of a force feedback haptic display is the rendering of contact between a virtual object and the virtual tool, and the subsequent coupling of the virtual tool to the physical device. There are various combinations of coupling techniques and contact modeling methods [1] to accomplish this task. The current demo showcases the ongoing work of our research group in exploring these techniques within a unified framework. This framework builds upon previous developments on energy-consistent rendering [2], and, it facilitates comparison and combined utilization of different methods using a generalized formulation that allows for adaptation according to the nature of contact events.
Fig. 1. A block diagram representation of the billiard demonstration’s modular components: device communication, simulation and contact model, and graphical display.
Improving Transparency through Device Orientation: In the context of Haptics, transparency indicates reduced device interference with the user’s sensation of the virtual world. Device interference originates from perceived weight and perceived inertia forces. Active reduction of perceived inertia is more challenging than gravity compensation since it requires access to, not only position, but velocity and acceleration level data. Reduction by modification of the mechanical design, on the other hand, is not feasible for every single new application and desired trajectory. Alternatively, it is possible to seek an ideal orientation in which the device interference is minimum along a desired path. A software developed by our research group at McGill was used to perform dynamic analysis of the Entact W5D along prescribed paths in the workspace. This software enables us to visualize inertia hyper-ellipsoids of dimensions greater than three and select device orientations that improve device transparency along paths of interest. Enhancing the Immersive Virtual Experience: Simulation of the entire virtual environment can be enhanced through the use of other sensory input to provide a more immersive experience. In this demo, we will show case how to employ workspace drift control [3] and computer vision-based tracking of the user to facilitate exploration of large virtual worlds with limited workspace devices. Combining these techniques with additional auditory input leads to a highly engaging virtual reality for the user
Fig. 2. Device orientation plays a key role in perceived inertia effects for working paths.
References 1. Constantinescu, D., Salcudean, S.E, Croft, E.A.: Haptic Rendering of Rigid Contacts Using Impulsive and Penalty Forces. IEEE Tran. Rob. 21(3), 309-323 (2005). 2. Mohtat, A., Kovecses, J.: Energy-Consistent Force Feedback Laws for Virtual Environments. J. Comput. Inf. Sci. Eng. 13(3), 031003, (2013). 3. Conti, F., Khatib,. O., Spanning large workspaces using small haptic devices. Eurohaptics Conference, 183-188, (2005).
