Comparing and Evaluating Menu Placement for Immersive Virtual Reality

Formative User Study

We carried out a within-subjects, formative evaluation study that produced preliminary results to identify design challenges faced by users who interacted with a two dimensional menu by comparing their menu placement: wall-fixed menu and controller-based pop-up menu. In the controller-based menu, the menu pops up on the left controller, and menu items can be selected using the pointer from the right controller (Fig. 3). The wall-fixed menu is fixed in a specific location and could be interacted with the pointer from the right controller (Fig. 2). Through this research, we aim to answer the follow-ing:

• RQ1: Does a controller-based menu or a wall-fixed menu provide a better user ex-perience in an immersive environment and why?

• RQ2: What are some of the design challenges faced by users when interacting withthe menu placed in wall-fixed vs. controller-based location?

The immersive VR environment in the study displays public health data over a map of a US state. The menu allows the user to interact with various system functions, such as resizing and repositioning the map and selecting various visual representations for the data.

Data Collection

We recruited six participants (3 males and 3 females) aged between 21 and 30 years who did not suffer from severe motion sickness. All of them were novice VR users and the average height was 5.5 feet. A researcher guided participants through a tutorial learning the Oculus Quest 2 controller to navigate the menu. Three tasks were per-formed to test the placement of menus, alternating their order of occurrence. The three tasks were: move the position of the map to fit a box in the VR space; display, collapse and hide all the bars; and find a specific zip code, display a stacked bar graph on the area and center it to your view. After each session, the participant filled out the NASA-Task Load questionnaire (TLX) and System Usability Scale (SUS) questionnaire. The task times were recorded and an open-ended, semi-structured interview was conducted in the end.

PDI - Power Distance in China, France, Japan, and United States

Preliminary Findings and Discussion

Task completion times

Mean values for task completion time per task by menu placement type.

The recorded task time of each participant includes interruptions such as Q&A, and not just task completion. Hence the data in Fig. 5 is descriptive and not statistically analyzed. For tasks 2 and 3, the wall-fixed menu had a faster task completion time than the controller menu. The longer time taken to complete the first task may show that learning time was longer for the wall menu, however, once learned, task completion was faster.

Task Load of Menu Use

Mean scores of NASA-TLX.

The NASA-TLX questionnaire is a measurement of task load. Fig. 6 shows higher task loads on all reported dimensions for the controller-based menu. Statistical results re-main insignificant due to limited data.

User Subjective Satisfaction

Mean values of SUS Questionnaire.

The SUS questionnaire measures user satisfaction based on user reported data. While statistical results remain insignificant, we found that there were some inconsistencies with the results. This may be due to the small sample size and the lack of statistical significance. For example, the wall-fixed menu had a higher score for questions of complexity and ease of use. These results are contradictory. While learning was higher for the wall-fixed menu, ease of use was lower. Once the users learnt how to use the wall-fixed menu, it was easier to use, as shown by Monteiro, et al.

Qualitative Findings

Wall-fixed Placement. Positive Feedback. Landmark: The fixed nature of the wall-fixed menu acted as a landmark where users knew where to find the menu. The display was also large enough for the user to view from any point in the VR space. P6 commented, “I liked the [Wall-fixed menu], it was large. It was fixed in one place. It's easy to like, you always know where it is relative to everything else. It's sort of useful like a directional marker if that makes sense.”.

Display size: Several participants pointed out that the large display of the wall menu made it easy to control the menu and increased accessibility. A participant mentioned,“I think for this application the wall one is better because it's bigger so it's easier to see and it's more accessible”.

Uninterrupted Visual Attention: The two focal areas of your vision are closer when using the wall menu. The user can view the map in their peripheral vision while using the menu. There is not much variation in the focus of attention when interacting with ite.g., “It's like using a TV remote. I can just look at the screen and I would move the map. I didn't have to continuously go back and forth between what I was doing and what I was selecting.”

Negative Feedback. Fixed Location: For certain tasks, the fixed nature of the wall fixed menu acted as a disadvantage. To move and map items was a challenge for P4 who commented, “So at times, if I'm doing a task, I cannot move the menu with me. So, the box (in task 1) is at the far left, and I would have to move and then check if I'm per-forming the right function.”.

Display Size: The large display of this menu occluded the map, which made it diffi-cult to interact with it. At times, when the map was resized to a smaller size, the wall-fixed menu appeared to dominate the VR space. A participant reflected, “[The wall-fixed menu] took the domination more than the map because it was bigger”.

PDI - Power Distance in China, France, Japan, and United States

Controller-based Placement. Positive Feedback. Proximity: When turned on, the usercan view the controller menu at an arm's distance which makes it appear closer to theeye, thereby, aiding better visibility e.g., “ ....It [controller menu] was closer to me.And the functionalities were more clearly visible.”.

User Control over the Menu: Having an on/off switch for this menu was useful for the user in two ways. First, it could be accessed from anywhere in the space. Two participants expressed that they had more control over the menu this way. Second, it pre-vented blocking the view of the map. Some reflections include:

P3: “If one angle wasn't working out for me, I could just move it to another angle toaccess it.
‍P4: “With the controller menu, it was good that I can turn it off when I don't need it.So it's not blocking the view or distracting me..”.

Negative Feedback. Physical Demand: Two participants found it difficult to operate asthey had to extend their left arm to view the menu clearly. One of them said, “.. con-troller menu was physically demanding when compared to the wall-fixed menu.”.

Disappearance: One of the participants who found it to be physically demandingtried to operate the menu by placing it closer to their body. The menu kept disappearingas a result and caused visibility problems.

Comparing Menu Styles. Overall, more participants preferred the wall-fixed menu (4participants) than the controller menu. In general, the awareness of the wall-fixed menulocation was useful. However, as the participant performed certain tasks, they realizedthat it obstructed viewing the map. The controller menu provided versatility by beingable to access it when needed and adjust the angle according to preference.

The wall menu was easy to control (using only the right controller). This may not be the best option for left-handed users. It was physically demanding to use the controller menu for people whose height was less than 5 feet 4 inches.

The display size of the wall-fixed menu made it easier to view it from a distance. It became uncomfortable when the user was standing too close to the menu or if the map was resized to be relatively smaller. The controller menu’s display was constant in size and closer to the eye. It helped with the user’s visibility. However, viewing the controller menu too close made it disappear.