Designing environment

This chapter will describe the building of the different scenarios that were used in the treatment of acrophobia. Since no one has any experience building environments where height is an important factor, it was decided to build the first application using prototyping. To prevent ourselves from building without any method, it was decided to use Foley's method.

The first section will describe the elevator using the four layered approach of the Foley method. Using these four layers, we formed an idea about what the elevator should look like. The next section will describe the hardware used to run the elevator, and how we helped to improve the realness of the environment with a simple gadget. The final section about the development of the elevator will explain the problems we had building a very simple user interface.

The section after the description of building the user interface will explain some of the conclusions we can draw about the perception of height. It will also describe knowledge that we gained which could be used while building the other environments. The final two sections will describe the other environments that were built.

Designing first environment

This section will describe how the elevator was built and some of the lessons we learned and could later use when building the other environments. The method of Foley is a four layered approach: Conceptual design, Semantical design, Syntactical design and, Lexical design. The following four sections will each describe one of the four layers of Foley.

Conceptual design

The virtual environment should give the user the sensation of height. To achieve this, the user is placed in a situation that in real life should also give a sensation of height. This real life situation is modelled as close as possible to reality.

Semantical design

The environment should give the user the idea that he is in control of the environment. To get this feeling he will be allowed to control the movement of the elevator, either up, down or stop. Unlike a normal elevator, where you only have control of the starting floor and destination of the elevator, now the user will have total control of the movement of the elevator. He will be able to stop it any point he likes.

To prevent the elevator from floating around in nothingness, it was placed in the Marriott Marquis hotel. The Marriott Marquis hotel is located in downtown Atlanta, Georgia, and is well known for its elevators.

The elevator itself was modelled very simply as being a square with a railing all around. The railing could then be used to hold the controls of the elevator.

Syntactical design

The syntactical design of the elevator is very simple. The user could only make the elevator go up, go down and stop. The person who controlled the elevator remotely, the operator, could do the following: Besides these extra controls for the elevator, the operator could, like the user, make the elevator go up, go down and stop.

This section will describe all the different states the elevator could be in. First the up, down and stop control state will be described and then the other controls of the operator.

UP, DOWN AND STOP

Both the operator and the user could control the movement and direction of the elevator. The user could do this to improve the sensation of height. The operator was able to change it as an emergency precaution. For instance, when the user could not find the stop or down button while panicking, the operator could help out.

There are two preconditions that have to be satisfied to be able to control the elevator: the elevator must be visible and the controls must be enabled. The following state transition diagram describes the different states the control can be in.

Figure 6.1: Elevator controls STD

ALLOW USER TO INTERACT

During normal operation, the user is allowed to control the elevator. Sometimes, however, the user should not be allowed to control the elevator. For instance, when the psychologist wants the elevator at a certain floor. Using this function the operator can switch the controls of the user on and off.

Figure 6.2: Elevator controls on/off STD

HIDE ELEVATOR

A function we came up with when we were discussing the elevator, was to hide the elevator. This function will probably not be used during the experiment. During demo days, this function can be used to remove the elevator from the scene, and have the user float in the air. By looking at the reaction of people, we had some test of the level of presence.

Figure 6.3: Hide elevator STD

CHANGE THE ELEVATOR SPEED

To get more control over the environment, the operator is able to change the speed of the elevator. Some people get more sensation of height when the elevator is moving at a high speed.

Figure 6.4: Change elevator speed STD

Lexical design

 The building was modeled after the Marriott Marquis in Atlanta, Georgia. The inside was built to give as many possible height clues as possible. The elevator is a floorboard with a railing all around it. On these railings, the controls can be placed. The controls are a red square to stop the elevator and green up and down arrows to move the elevator up and down.

The buttons have an auditory feedback so that the user can tell that he pushed the button. When pushing the stop button, the user will hear the word "stop". Pushing the up button, the user will hear "up" and, pushing the down button, the user will hear "down".

The hardware used

The first few models that were built could be run on an SGI Indigo Elan. But very quickly we saw that this machine was not powerful enough for the applications we were going to build. Especially texture mapping, which helped to improve the models, asked too much of the Indigo Elan. Now the Indigo Elan was only used to get the information from the trackers and send it to an SGI Reality Engine and receive from the Reality Engine commands to play sound. The Reality Engine had no sound capabilities. Figure 6.5 shows the setup that was used when testing the environments.

Figure 6.5: Hardware setup testing

When testing the models, a simple square board was placed on the ground to show the user the range of the "flock of birds". People walking around on the board would occasionally step off the board. To some people, this difference in height, about 1cm or 0.4", made such an impression that it was decided to build a mock-up of the elevator (see Figure 6.6). An advantage to this mock-up would also be the fact that people could touch the railing they saw in the virtual environment, a sort of tactile feedback.


Figure 6.6: Mock-up of the elevator

Treatment and environments Designing environment (2) TOC
Rob Kooper
 kooper@cc.gatech.edu
Last modified: Sat Apr 1 15:06:21 1995