Immersive virtual environments (VEs) provide participants with computer-generated environments filled with virtual objects to assist in learning, training, and practicing dangerous and/or expensive tasks. But does having every object being virtual inhibit the interactivity and level of immersion? If participants spend most of their time and cognitive load on learning and adapting to interacting with virtual objects, does this reduce the effectiveness of the VE? We conducted a study that investigated how handling real objects and self-avatar visual fidelity affects performance and sense of presence on a spatial cognitive manual task. We compared participants' performance of a block arrangement task in both a real-space environment and several virtual and hybrid environments. The results showed that manipulating real objects in a VE brings task performance closer to that of real space, compared to manipulating virtual objects. There was no signifi-cant difference in reported sense of presence, regardless of the self-avatar's visual fidelity or the presence of real objects.

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We present algorithms that enable virtual objects to interact with and respond to virtual representations, avatars, of real objects. These techniques allow dynamic real objects, such as the user, tools, and parts, to be visually and physically incorporated into the virtual environment (VE). The system uses image-based object reconstruction and a volume query mechanism to detect collisions and to determine plausible collision responses between virtual objects and the avatars. This allows our system to provide the user natural interactions with the VE.We have begun a collaboration with NASA Langley Research Center to apply the hybrid environment system to a satellite payload assembly verification task. In an informal case study, NASA LaRC payload designers and engineers conducted common assembly tasks on payload models. The results suggest that hybrid environments could provide significant advantages for assembly verification and layout evaluation tasks.

Immersive virtual environments (VEs)

This paper focuses on effect of elevated temperature on recycled aggregate concrete. When concrete is exposed to Elevated Temperature due to fire, the property of a concrete may alters. The effects of elevated temperatures on the physical and mechanical properties of various Recycled aggregate concretes are explained Here w/c ratio 0.27 and 0.36 with replacement of 0%, 30%, 35%, 40%, 45% and 50% of Natural aggregates by Recycled aggregates are taken into consideration. Here 35 specimens (Cubes, Cylinder and prism) for each trial mixes (12 nos) has been casted and heated under four different temperature: 200 0 C, 400 0 C, 600 0 C and 800°C.. Attempt is made to compare with different mixes of recycled aggregate concrete. The results indicate that concrete with aggregate partially replaced with RCA exhibits good performance under elevated temperatures and it can be considered comparable to conventional concrete.