Summaries for week 2
Merging Virtual Objects with the Real World: Seeing Ultrasound Imagery within the Patient
This paper is about a 3D ultrasound system for real time 3D volume data displayed within the subject, viewed with a HMD.
Up to now, ultrasounds were used because they were the best solution since they are safe and real time, but the quality is poor and there is a lot of noise. The aim is to have a real time 3D acquisition (on which studies have already been made) and a real time 3D display, which can be made for the while with post low pass filtering but it is slow. To achieve this, three steps have been followed. The first has been to develop algorithms to acquire and render data, the second has been to design a virtual environment and the third step has been to recover structural information for volume rendering.
To have a real time display, an incremental volume visualization is used. From the age of each voxel, a coefficient is computed and used in an ARMA filter.
The position and the orientation of the HMD are defined by six degrees of freedom. These position and orientation as the ultrasound images produce the 3D display. The calibration is performed with a transducer transformation (position and orientation of the tracker) and a camera transformation (position and orientation of the HMD).
Tests have been led on a woman who was 38 weeks pregnant and have been quite conclusive.
However, there are several technical problems. First, the images are displayed on top of the subject and not within him. A partial solution has been found, which is to display a virtual hole. Then, there is a lag for the synthetic images. Also, the quality of the tracking system (Polhemus) is not good enough, and finally the image resolution is not satisfying.
Other applications could be in the field of surgery or architecture, and to display plans of building or technical information.
This kind of virtual environment is very interesting because virtual objects are merged with the real world, but they actually represent real objects and are displayed at the location of these real objects. Thus, it gives us access to pieces of information which were already present, but non noticeable for us. To improve and clarify the display, could an enhancement be that the program generates and displays information over the 3D image?
Virtual Environments for Treating the Fear of Heights
The difference between virtual environments and common interfaces is the degree of immersion. Thus, immersion is the key for a good virtual environment, which is here used to cure (or help with) acrophobia. Two points are studied : the efficiency of the immersion and the efficiency of the therapy.
The process of an in vivo therapy is to evaluate which situations the patient is afraid of and then to gradually habit him to these situations. Imagination can also be used to treat phobias. The goal here is to reproduce these situations in virtual environments.
The system used is a monoscopic vision, which allows to display more details and a more realistic environment. Three environments have been designed. The first one is an open elevator with a wooden platform for better sensations and a tactile feedback. The subjects can command the elevator thanks to a tracker in their right hand. The second environment is made of balconies, there are four different heights and the wooden platform is still used. The third one is made of bridges above a canyon in which flows a river. There are three different heights of bridges, their shapes and steadinesses are also different. The patient can also go to the top of the canyon to observe the whole scene.
For the experiments, the first step has been to identify which patients are acrophobic with a questionnaire. Among 478 students, 17 have been selected and completed the study. Another criteria was also not to panic with an HMD. During the experiences, the therapist was seeing the same scene as the subject in order to analyze the situation and bind it to the patient’s feelings. After the treatment, the same questionnaire was answered by the subjects.
For the results, SUD ratings have been used and show that he subjects were immersed as if they were in a physical situation. Furthermore, symptoms have been recorded (sweat, heart palpitations, …). Positive feedbacks also came from the students. However, many patients had nausea because of simulation sickness, since what was displayed was different from what their senses indicated.
Three only one subject for whom the therapy has not been conclusive but he had bad eyesight and the resolution of the HMD was not good.
Finally, the questionnaires showed that the therapy has been a success.
Thus, virtual environments are a good alternative to imaginative therapy and can be used to simulate extreme situations.
These virtual environments seem to be very efficient against acrophobia, and should have been improved since 1995, but would/could virtual environments be effective for all phobias (for instance arachnophobia)?
Designing Interactive Theme Park Rides
This paper deals with augmented reality rides, in this case Pirates of the Caribbean at Disneyland. The question they address is “How to design an enjoyable ride?”. The key is to have a trade-off between the freedom of the player and a great adventure.
First, to make the player avoid dull places during this short game, there are architectural points of interest and the ships (to be shooter) attract the player. Furthermore, sneak attacks occur when no boat is in range and the ship of the player is teleported back if it is too far from the play field.
Concerning the pace, planned events occur at certain times to ensure an exciting pace and a climax.
The user interface has also to be intuitive. Colors and physic rules are adapted for ease of play, a good visibility and a non boring game. Also, the AI is more designed for the show than for providing the best strategy, so that the ride is exciting.
Finally, the immersion is enhanced with surrounding sound, and the fact that players have to run on the ship allow a physical interaction.
To achieve that, guest testing has been led and reprogramming has been made during the game in order to have a ride enjoyable for small groups, which shows the importance of knowing the target the product is made for.
This paper shows the importance of knowing who will use the product, and what is the best for the users, although technological trade-offs have almost always to be made for a greater pleasure. However, depending on the groups (for instance their ages or their genders), other settings like difficulty, number of actions/possibilities or a slightly different story could be changed to offer them a custom experience. Thus, could the game be different for each group or even for each player?
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