Bo Pang’s Week 2 Summaries

Merging Virtual Objects with the Real World: Seeing Ultrasound Imagery within the Patient

This paper describes Bajura and his colleagues’ research on 3D ultrasound image acquisition and display and introduces two real-time 3D ultrasound systems developed by them.

The authors first reviews previous work in 3D ultrasound technique.  Since 3D ultrasound scanning system is not available by that time, 3D ultrasound image need to be reconstructed from 2D slices. The authors then describe a 3D volume data visualization approach called “incremental volume visualization” where the visualized 3D volume is constructed by applying a 4D convolution process on a registered 2D ultrasound image sequence. This visualization technique is tested by their first system. 2D image sequence is acquired from a mechanical tracking arm with 3 DOF and a 3D view of the whole object can be rendered after reconstruction and visualization.

The authors also introduce their second 3D ultrasound system with a video see-through head-mounted display (HMD). This system merge ultrasound echography image with real world objects where the ultrasound echography images are displayed in their 3D position in the real world. Images are acquired by an echography scanner with a tracking system mounted on the transducer. The tracking system can get the 3D position and orientation (6 DOF) of each image. These information is used to get the position and scale of 2D ultrasound image pixels in 3D space. The video see-through HMD captured the real-world by head-mounted TV cameras then combines the real-world image with ultrasound images rendered by the computer. HMD is also tracked by the same tracking system.

At last, the authors describe the technical problems in their virtual environment such as system lag, display resolution, tracking system range and stability etc.  Many of these problems are still exist in most virtual environment applications.

Questions: When using this kind of system in a real diagnose process, is the accuracy of the tracking system good enough to help the doctor make the correct diagnosis?

Virtual Environments for Treating the Fear of Heights

The main difference between virtual reality and interactive computer graphics or multimedia is the immersion, where virtual reality can make users feel a strong sense of presence. This paper shows an example of using VR technology to conduct exposure therapy of individuals with psychological disorders.

These researchers build virtual environments for treating acrophobia. This virtual environments system is used for creating a serious of virtual scenes for the patient to go through a process of exposure and adjustment to these situations. Three different virtual environments are created which are an elevator, a series of balconies and a series of bridges. These virtual environments are displayed by head-mounted display.

The study subjects are selected from two Atlanta universities and 20 students who were identified as possible acrophobia enter the study and 17 complete the treatment. Subjects are divided into a treatment group and a control group. The treatment for treatment group is conducting several sessions of individual VR graded exposure. Results are evaluated by compare the pre-treatment assessment and post-treatment assessment.  Results shows that for the treatment group, anxiety, avoidance, distress and other attitudes towards heights decreased significantly from PRE to POST. Moreover, 7 of 10 subjects who completed treatment reported that they also felt better when they exposed themselves to height situations in real life, which prove the treatment is actually useful for real life.

Question: Is the reality of virtual scenes an important factor in the treatment?

Designing Interactive Theme Park Rides

This paper talks about the design of an interactive theme park ride called Pirate of the Caribbean – Battle for the Buccaneer Gold.

An interactive virtual reality game keep a balance where on one hand players can control their adventure and do they want in the game, on the other hand, no matter what they do they can still have a great experience. This paper first introduces several mechanisms in this game to keep that balance such as using architectural weenies, guide ships, sneak attacks and waterspout. These mechanisms guide the guest to go to interesting place in different ways. Then the authors talk about another important factor of this kind of game, providing intuitive user interfaces.  They mention that for a virtual reality game to play with, it is more important to be fun than being realistic. Virtual reality games need to create a convincing virtual world. Like this game, guest should able to feel the world with their eyes, their ears, as well as their body. Stereo display, 3D surround sound and motion base as well as physical experience such as running from cannon to cannon, these features give guest unique experience of being a pirate. At last, this paper also talks about their iterative design strategy when designing the game.

Question: In the game in this paper, there are two main physics user interfaces, steering wheel and cannons. Increasing the number of physics user interfaces can increases the gameplay of the game but could also make the game more complicated. How do we balance these two things?

 

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