[Week2 Summaries] Bajura: Ultrasound, Hodges et al: Fear of Heights, Schell et al: Theme-park VR

Merging Virtual Objects with the Real World : Bajura et al.

In the paper Merging Virtual Objects with the Real World : Seeing Ultrasound Imagery within the Patient, the authors describe the implementation of their system that composites images slices obtained via 2D Echography (2DE) onto real-world video obtained by a mounted TV camera using a see-through HMD.

The authors also give an overview of their research on an incremental 3D ultrasound visualization technique. The described technique combines 2D image-slice data obtained from 2DE scanners, incrementally, as it is received, using this to update a 3D scalar field that is then rendered using volume rendering by ray-casting.

The use of a HMD and a mounted TV camera to register and overlay [1,..,n] 2DE image slices onto read world video constitutes the major body of the authors’ works, and some of their significant contributions are:

  • Registration of the 2DE image slices to their true 3D locations by the use of 2 appropriately calibrated receivers to track with 6 degrees of freedom, both the ultrasound transducer and the HMD.
  • Synchronization of the display architecture to achieve separation of display update rate from the image data acquisition rate, thus enabling registration to be clocked to the display update cycle.

In concluding, the authors motivate further investigations in the field by specifying the major challenges that still remain unaddressed, primarily, the technical problems that arise when trying to provide better visual cues as opposed to a simply overlaying the synthetic image slices over the real-video, and the lag that results in perceptible artefacts and prevents the system from being a convincing experience.


Virtual Environments for Treating the Fear of Heights: Hodges et al.

In the paper Virtual Environments for Treating the Fear of Heights, Hodges et al. describe the user study that they carried out to treat a set of subjects experiencing acrophobia by graded exposure in a virtual environment. The authors distinguish their work from other similar studies by incorporating detailed assessment tests for the efficacy of their treatment.

The authors describe the construction of the 3 virtual environments, simulating the experiences of an elevator ride, standing on top of outside balconies of tall buildings and standing on bridges spanning canyon edges, which they brought to life using textured monoscopic images.

The appropriately selected treatment group were assessed on rubrics including the acrophobia questionnaire, pre and post the treatments – a metric capable of detecting improvements in subjects. The subjects were also requested to report their anxiety levels during their therapy sessions on a scale of 0-100.

The results of the user study revealed that prolonging exposure to the virtual environments did result in a corresponding reduction in the anxiety levels of the subjects, much akin to the results noted in studies where people had been subject to in-vivo graded exposure. The results also compared favourably to systematic desensitization studies. The results thus enabled the authors to assert that their designed Virtual Environments enabled their subjects to experience presence in them and could find widespread application for the treatment of psychological disorders.


Designing Interactive Theme Park Rides: Michael Macedonia and Lawrence Rosenblum

In the paper, the authors describe how they brought to life the interactive theme park ride Pirates of the Caribbean – Battle for the Buccaneer Gold, which is installed at DisneyQuest Orlando and DisneyQuest Chicago.

The nature of an interactive theme park ride makes stringent demands on elements of fun, engagement and other such factors that contribute towards the feeling of getting one’s money’s worth. To this end, the authors describe how the clever placement of Weenies allows them to nudge the budding buccaneers along the well-crafted virtual reality experience, while making them feel very much in control of their choices, and thus preventing it from being a discernible scripted experience. The authors also describe how they bring the experience to a scripted timed climax, ensuring timely disembarkment by current occupants of the virtual pirate-ship and also increasing replayability.

The authors describe the additional efforts they undertook to help create an immersive, “almost real” experience, including intuitive user interaction, haptic feedback and hi-fidelity aural accompaniment.

To conclude, the authors mention how employing iterative design techniques allowed them to concentrate on initially getting the game dynamics just right and then adding other bells and whistles. They also stress on the importance of considering the target audiences’ expectations while designing similar experiences.