Spatial Perception in Virtual Environments:
Evaluating an Architectural Application

CHAPTER 6. RUNNING THE STUDY.

Preparation - General.

With regard to all four experimental conditions, the only general concern was that the selected site for the study remain unknown to the participants. It was feared that some participants might be tempted to visit the museum before the study. That, of course, would have tainted the results. Ideally, in a pre-selection process, only architects who had never been to the Henry Art Gallery could have been selected for the study. Unfortunately, most designers have been at least once to the museum. After their selection, care was taken to meet them far away from the test site so as to keep it a mystery.

Preparation - Novelty Factor in Simulations.

For the simulation conditions, additional preparation was required. There is legitimate concern that people who discover virtual environments for the first time are under the spell of the technology's novelty. Furthermore, the SpaceBall they would be using to control their movement is highly unusual, and it was important they have a chance to practice using the device. In general, regardless of the type of experiment, it takes participants a certain amount of time to adapt to the new environment. The environmental psychologist Proshansky suggest that a person's perception of space "is greatly modified as (they) adapt to an environment..." (Proshansky 1970). Proshansky's remark suggests that participants should be allowed enough time to adapt to the simulated environments for their perception of the space to stabilized.

For all of these reasons, a simple model was constructed in which participants could get acquainted with the simulated environments and using the Spaceball. This model consisted of a floor, a few columns and walls and a winding line which represented a path. As participants followed the path, the columns made way for more and more walls and the environment became increasingly inclusive. It became a sort of maze-like space. Participants' task was to follow the colored path to the core of the maze and back out again until they felt sufficiently comfortable using the interface.

The Setup.

In all simulation conditions, participants were asked to stand because it is a more engaging position in which to discover an architectural space then when seated. Sasanoff, in his study of a film simulation technique argues that the posture can affect the behavior of the participant : "the comfort of viewing (sic) the museum while seated in the chair may increase the propensity of the observer to seek a broader rage of experiences than might be the case in the real world experience" (Sasanoff 1966). Since participants were walking in the Real condition, then they at least had to be standing in the simulation conditions.

In the Monitor condition, participants stood in front of a large television monitor. Their distance from the screen was 18". This insured a field of view of 90deg., which was consistent with the combined field of view of both eyes in the eyephones conditions. The height of the viewpoint was fixed at 5' 8", regardless of the height of participants. An average eye height was taken because it would have been too difficult to adjust it for every new subject. The fixed eye height was never different from participants' actual eye height by more than six inches. Participants controlled the direction they were looking as well as their movement with the SpaceBall. It was constrained to permit Yaw and Pitch of the view point (no Roll), and movement only in the direction one is facing (no reverse and no sliding sideways).

The Fixed condition the setup was similar to the Monitor condition. The eye height was also fixed at 5' 8". They controlled their viewpoint and movement exactly like in the Monitor condition as well. However, instead of looking at a monitor, these participants were wearing the stereoscopic eyephones.

In the Tracked condition, the tracking device automatically adjusted the participants' viewpoint to the exact height of the participant's eyes. Like in the Fixed condition, they viewed the model through the stereoscopic eyephones. To move in the model, participants pushed on the Spaceball and moved in the direction they were looking just like in the other conditions. However, participants in the Tracked condition controlled the direction of their view by actually turning their head.

The Walkthrough.

In all four viewing conditions, participants visited the spaces in the museum in a pre-determined order. This was to control for variations in results due to differences in the way people explore new spaces. The tour of the museum was such that each space was visited at least once. At specific locations in selected spaces, participants would be asked to do one of the several estimation tasks. Figure 6.1 below shows the path through the museum, as well as the three locations where participants were asked to estimate a room size.

Fig. 6.1 - Locations of size estimate task.

Figure 6.2 shows the location of the three pointing tasks. Because of the narrow field of view in the simulation conditions, all the estimates were made form the corners of the rooms. In this way participants had a little bit more spatial information for making their estimates.

Fig. 6.2 - Location of pointing task and path of visit.

Participants entered or started the visit in the middle of the entrance hallway (space "B" in Fig. 6.3). In the simulation condition, their viewpoint was automatically positioned there. In the real museum, they were accompanied to that point. The next room on the visit was the one on the left (space "A" in Fig. 6.3). It contained a television monitor. Participants were asked to remember its location because they would be asked to locate it later. Then they were asked to move to the corner on the far left, to turn around and to estimate the dimensions of the room without moving from that location (Fig. 6.1). They could describe the dimensions of height, width and length in any order.

Fig. 6.3 - Plan of museum and labeled spaces.

Then, they were taken back out of the room and into the main gallery (space "D" in Fig. 6.3). In the model, this room had one chair and an adult scale figure holding the hand of a child scale figure. I served as the scale figure in the real museum. Upon entering this space, participants were asked to express their first impressions of the main gallery. Their response was recorded on tape. They were then led to the room ahead on the right which contained the second television monitor (space "F" in Fig. 6.3). They continued on through it until they reached the end room (space "G" in Fig. 6.3). This space had a scale figure next to a chair.

There, as in the first room, they were instructed to go to the corner and estimate the dimensions of the space (Fig. 6.1). Then they did the first pointing task. They were to point in the direction of the first television monitor (Fig. 6.2). Next, they were led to the other end of this room and into the following room (space "E" in Fig. 6.3). This room had one scale figure. They traveled through this room and re-entered the main gallery. Once back in this space, they went to the far right corner and pointed to the second t.v. monitor (Fig. 6.2). They also estimated the size of this room (Fig. 6.1). They were asked to remember this space because they would be asked to describe it in the questionnaire.

Then, they were taken through the hallway and into the last remaining non-visited space (space "C" in Fig. 6.3) where again, going into the far right corner, they estimated the direction to the scale figure and chair in the end room (Fig. 6.2). That concluded the visit.

After the tour of the museum, participants were invited to fill out the questionnaire. This took about 45 minutes and they were asked to do the following task: (1) Draw a sketch plan of the spaces previously visited, (2) describe the main gallery, (3) evaluate the interface, (4) evaluate your sense of presence, (5) participant profile ( Appendix: A. Questionnaire). The entire experiment took about 1 to 1 1/2 hours per person.

Notes on differences in set-up: there were a few differences between the Real and the simulated visit. In the Real condition, the position of the participants during the estimation tasks in the end room and the main gallery were slightly different. In general, they were not as close to the corners of the rooms. The need to place participants in the corners did not become apparent until the simulation conditions were run. Also, instead of television monitors, participants in the Real condition had to locate different colored chairs. The monitors required fewer polygons to describe in the model. However, chairs were the only available objects in the real museum.