Experimental Setup and Procedure

The experiment used the VisionSpace system mentioned in Chapter 1 and Figure 4.2.3 shows the experimental setup.

Figure 4.2.3. Top down view of the experiment setup (left) and experiment Setup (right)

At the beginning of each condition, the participants were asked to stand at the center marked on the floor. When the experiment started, a large cube comprising of 3 by 3 images on each surface was displayed on the large display. Each image was a warped or color-filled square as shown in Figure 4.2.4. The warped square images and color-filled square images were placed randomly on the surfaces of the cube in each task. Based on the users' position and the tracking technique, the position and rotation of the cube could be changed. For example, when the PoV moves left, the left side of the cube

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would be displayed. The right side of the cube would be displayed when the PoV moves right. With OST, the position of the cube would be shifted according to the location of the PoV.

Figure 4.2.4. An example of a cube consisted of 3 by 3 warped square (left) or color-filled square (right) displayed on the large screen. As shown Figure 4.2.5, the tablet displays the location of the target image in the cube (on the left side) and four answer images (on the right side). The gray squares indicate a planar figure of each side of the cube in the large screen display, which does not include the back surface. The left image in Figure 4.2.5 is the example of warped squares on the cube. The right image in Figure 4.2.5 is the example of color-filled squares on the cube. Additionally, the author marked the location of the cube in the right image (top(T), bottom(B), left(L), right(R), and center(C), please note that these notations were not presented during the experiment).

Figure 4.2.5. The graphic user interface on a user's tablet. The participants can move around in the VE to find the target image in

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each condition. If the participants find the target image on the large screen and then select the identical shape or color among the four answers displayed on the tablet, one task is completed.

The detailed procedure of the task is explained in Figure 4.2.6. When the experiment started, the screen on each mobile tablet displayed the graphic user interfaces shown in Figure 4.2.5. The participants were asked to find the surface containing the 'X' mark in the planar figure on the mobile tablet (Step 1 in Figure 4.2.6). After identifying the surface, the participants were asked to find the same surface of the cube on the large display screen (Step 2 in Figure 4.2.6). Based on the users’ movement, the cube on the large screen showed different sides of it as the user’s head is tracked to control the PoV. Therefore, the five visualized surfaces (left, center, right, top, and bottom surface) of the cube could be explored by the user movement. In step 3, the participant was asked to find the same section on the identified surface, divided into a 3 by 3 grid where the 'X' mark was placed. As shown in step 3 in Figure 4.2.6, on the mobile tablet screen the 'X' mark was shown on the left bottom of the left surface. Therefore, the participants needed to find the corresponding location on the cube shown on the large screen display and identify its color, which is orange in this case. The dashed circles indicated corresponding grids on the same surface. To complete the task, the participants needed to select the corresponding color/shape and press the 'Confirm' button on the mobile table screen. This is the process of a single task for the experiment. The participants were asked to repeat the task 12 times for each condition.

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Figure 4.2.6. Procedure of the single task including 4 steps in the experiment

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Table 4.2-I summarizes the expected users’ movement based on target position. The author defined 12 possible user movements that create a natural flow of movement in the tracking space. The experimental tasks in each condition started from one of the four tasks: No 1, No 4, No 7, or No 10. The starting task for each experimental condition (ME, WE, MOS, and WOS) was assigned randomly for counter-balancing. Once a starting task number was selected, the rest of the following tasks were decided as a consecutive task number as shown in Table 4.2-I. For example, when task No 4 was a starting task, the following 12 tasks (No 4, 5, 6, 7, ..., 12, 1, 2, 3) were sequentially conducted by a participant.

Task No 1, 2, 3, 4, 5, and 9 are used to evaluate the proposed techniques in the worst-case scenario mentioned in Section 4.2.2.2 and to investigate how users can solve the worst-case scenarios and how the interaction techniques can support or disturb users in worst-case scenarios. In the tasks, the PoV is fixed when users travel opposite direction simultaneously. However, to complete the task, participants need to discuss with a partner, so that they can travel sequentially or together in the same direction.

Table 4.2-I. The target location on the cube and expected movement for the experimental tasks (L: Left, R: Right, and C: Center)

Task No.

User 1 User 2

Target

Position Movement Position Target Movement

1 Left L ← C Right C → R 2 Right L → C → R Left L ← C ← R 3 Center C ← R Right L → C → R 4 Right C → R Left L ← C ← R 5 Center C ← R Center L → C 6 Left L ← C − R Left L ← C 7 Right L → C → R Right L → C → R 8 Center C ← R Left L ← C ← R 9 Left L ← C Center L → C

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10 Center L → C Right C → R

11 Left L ← C Left L ← C ← R

12 Center L → C Center L → C

Before each condition, participants practiced the tasks and the four different tracking techniques until they were familiarized. This took about 10 to 15 minutes. The participants were requested to refrain from unnecessary movement for the tasks and to complete the tasks as fast as and as accurate as possible for the experiment.