IN DEGREE PROJECT MEDIA TECHNOLOGY,SECOND CYCLE, 30 CREDITS

, STOCKHOLM SWEDEN 2017

Performance of Amplified Head Rotation in Virtual Reality under Different Object Distances

JONNA KARLSSON SELLÉN

KTH ROYAL INSTITUTE OF TECHNOLOGYSCHOOL OF COMPUTER SCIENCE AND COMMUNICATION

Performance of Amplified Head Rotation in Virtual Reality under Different Object Distances

JONNA KARLSSON SELLÉN 

 

Master of Science (in Engineering) in Interactive Media Technology

Master’s Thesis in Interaction Design (30 ECTS credits)

Royal Institute of Technology (CSC) year 2017

Email to Author: jonnaks@kth.se

Supervisor: Anders Lundström

Examiner: Ann Lantz

2017-06-20

ABSTRACT

VR headsets commonly used today is providing the user with a limited field of view of about 100°, which is narrow compared to human's field of view of about 200°. One way to overcome this limited field of view is to amplify the virtual head rotation. Little research has evaluated how different settings of amplified virtual head rotation are affecting performance during object selection when varying the distance between the user and the object. Therefore, the aim of this study was to look at how different amplification settings (no amplification, factor 2 amplification and factor 3 amplification) affected object selection for objects placed at distances of 5, 10 and 20 meters, measuring performance in accuracy and time.

In conclusion, an amplification of a time 2 factor was the fastest one when selecting object at a distance of 10 and 20 meters. For 5 meters, an amplification of times 3 was the fastest. In accuracy, amplifying the virtual head rotation times 1 (no amplification) was the most accurate one when selecting objects at a distance of 5 and 10 meters. An additional interview revealed that test subjects perceived the no amplification as natural but slow and the times 2 amplification as both natural and fast, while the times 3 amplification was generally perceived as too fast and difficult to focus with on objects at all distances.

SAMMANFATTNING

De vanligaste VR headseten som idag används för virtuell verklighet, förser användaren med ett begränsat synfält på 100°, vilket är smalt jämfört med människans synfält på 200°. Ett sätt att överkomma denna begränsning är genom att förstärka den virtuella huvudrotationen. Få forskningsstudier undersöker hur olika förstärkningar på den virtuella huvudrotationen påverkar objektselektion under varierande avstånd mellan objekt och användare. Därav presenteras i denna rapport en studie som undersöker hur olika förstärkningar (ingen förstärkning, faktor 2 förstärkning och faktor 3 förstärkning) påverkar objektselektion, mätt i tid och precision, för objekt placerade på 5, 10 och 20 meters avstånd.

Resultatet visar att en förstärkning av faktor 2 ger den snabbaste selektionen av objekt placerade på 10 och 20 meters avstånd. För objekt placerade på 5 meters avstånd är en förstärkning av faktor 3 snabbast. När det kommer till precision, tyder denna studie på att ingen förstärkning ger den mest precisa objektselektionen på 5 och 10 meters avstånd. En kort kompletterande intervju visade att testdeltagarna upplevde ingen förstärkning som naturlig men långsam, en faktor 2 förstärkning som naturlig och snabb, och en faktor 3 förstärkning som för snabb och svår att fokusera med på samtliga objektdistanser.

Performance of Amplified Head Rotation in Virtual Reality under Different Object Distances

Jonna Karlsson Sellén MSc student in Interaction

Design at CSC department KTH Stockholm, Sweden

jonnaks@kth.se

ABSTRACT VR headsets commonly used today is providing the user with a limited field of view of about 100°, which is narrow compared to human's field of view of about 200°. One way to overcome this limited field of view is to amplify the virtual head rotation. Little research has evaluated how different settings of amplified virtual head rotation are affecting performance during object selection when varying the distance between the user and the object. Therefore, the aim of this study was to look at how different amplification settings affected object selection for objects placed at distances of 5, 10 and 20 meters, measuring performance in accuracy and time. In conclusion, an amplification of a time 2 factor was the fastest one when selecting object at a distance of 10 and 20 meters. For 5 meters, an amplification of times 3 was the fastest. In accuracy, amplifying the virtual head rotation times 1 (no amplification) was the most accurate one when selecting objects at a distance of 5 and 10 meters. An additional interview revealed that test subjects perceived the no amplification as natural but slow and the times 2 amplification as both natural and fast, while the times 3 amplification was generally perceived as too fast and difficult to focus with on objects at all distances.

Author Keywords User experience, amplified virtual head rotation, performance, distance, virtual reality

INTRODUCTION Virtual reality (VR) has in recent years become an upcomer within new technologies and the future looks bright for VR technology. One of the main driving forces behind the success is the Head Mounted Display (HMD). VR has put several interaction methods in a new context. Today, the dominating mode of interaction is handheld controllers, reminiscent of the video game era. Another solution uses sensors attached to the body to detect physical movement and translate these into the virtual world. One interaction is the head rotation. Usually, users look around in the virtual environment (VE) with their natural head rotation. This means that there is no difference between the head rotation in the virtual and physical environment (Kopper et al., 2011).

The natural head rotation used in VR is affected by the

HMD. The flat displays used today in the most common HMD offer a field of view (FOV) of around 100 degrees while the human FOV is closer to 200 degrees (Warren et al., 1990). This ultimately means that the user needs to rotate the head more than what would be required in reality to compensate for the narrower FOV (Baber et al., 1999). Accordingly, the HMD forces the user to exert a greater amount of muscular activity to assimilate the same amount of visual information (Baber et al., 1999).

One way to compensate for the narrower FOV, is to add an amplification to the virtual head rotation (Kopper et al., 2011, Jay et al., 2003). Amplifying the virtual head rotation means that the head in the virtual world rotates faster than the actual physical head rotation. This has the potential to offset the problem of excess movement related to FOV.

Amplified virtual head rotation (AVHR) is often perceived as natural (Ngoc et al., 2011), which could be explained by visual dominance, i.e. the phenomenon that vision is the most dominant sense among humans. Earlier studies (Jay et. al., 2003, Poupyrev et al., 1999, Waller, 1999) confirm that users find AVHR intuitive when rotating in VR and searching for objects. In addition, different methods of AVHR seem to, to some degree, improve performance when selecting or counting objects in the virtual world (Jay et al., 2003). Additionally, decreased fatigue have been reported (Jay et al., 2003).

When it comes to performance in object selection for VR, the selection must be rapid and accurate (Argelaguet et al., 2012). Other performance measures, such as 3D search abilities in VR, the ability to find objects, can be measured by counting the numbers of found objects during a fixed time interval (Ragan et al., 2016). In flight simulator training, performance is measured by the ability to handle a difficult aviation situation by judging pilot performance (Luan et al., 2013).

It is known that object selection is affected by the distance to the object in question (Chadwick et al., 2005). The time to select an object is positively correlated with the distance to the object and (that the selection is less accurate if the time to selection decreases) negatively correlated with the accuracy of the selection. However, little AVHR research

has been made regarding object selection performance for varying distances to objects.

Due to the shortage of research on the matter, the aim of this paper is to explore how time and accuracy in object selection is affected by distance in AVHR. This is studied through a user study in which the participants had to select objects at different distances in VR for three different AVHR settings ranging from no amplification to three times amplified head rotation. To further deepen the understanding of the collected performance measures user experiences was also collected through interviews.

RESEARCH QUESTION AND HYPOTHESIS How is object selection performance, in terms of speed and accuracy, affected by different AVHR settings and distances to objects?

The first hypothesis was that a higher amplification would decrease accuracy in selection of objects since fine tuning are more difficult, especially for object placed at a large distance. The second hypothesis was that a higher amplification would make selection of objects in the close surrounding faster because no fine tuning was needed. For objects in a larger distance a high amplification would make the selection slower since the objects are smaller which makes fine tuned selection more difficult.

BACKGROUND The amplification in AVHR can be achieved through either linear or nonlinear mapping. A linear mapping is represented by an AVHR that is increasing by a certain factor, normally a 2 times (x2) or one and a half times (x1.5) factor for each angle. In other words, a x2 amplification of the AVHR on a physical head rotation of ten degrees to the right results in 20 degrees head rotation to the right in the VE. A nonlinear mapping of AVHR works similarly but the amplification is either decreasing or increasing with for example an exponential or a cubic growth. For instance, if increasing the AVHR with a cubic growth of 1.15 (y = x1.15), a physical head rotation of 10 degrees will results in a AVHR of 14.13 degrees.

Figure 1: Showing the rotation axis; yaw, pitch and roll. For example, when rotating your head from the left to the right, the head is rotating around the yaw axis.

The amplification could both be applied to the yaw (the head rotating around the vertical axis) rotation or the pitch (the head rotating around the horizontal axis) rotation (Ragan et al., 2016), see figure 1. Since the human horizontal FOV is larger and more commonly used than the vertical FOV when exploring the VE, more research has been done when amplifying the rotation around the yaw axis. In one study (Jay et al., 2003), there was a significant improvement in task performance; searching, finding and selecting objects when adding a x2 linear amplification on the virtual head rotation around the yaw axis compared to a x1 head rotation(non-amplification). In this case, the objects were placed outside the immediate FOV and performance was measured by the time (sec) it took to finish the trail.

According to another study (Kopper et al., 2011), adding an amplification had a significant effect on performance when counting objects in a VE using an HMD. In their study, the FOV was 102 degrees, whilst the amplification was linear and varied between x1, x2 and x3 amplification. The study showed that the x3 amplification lead to lacking counting performance. No significant difference in counting performance could be seen between the x1 and x2 amplification. The performance was measured in number of objects counted during a specific trial.

Object selection is fundamental when interacting in VE and is an area that is important to improve and study further. When measuring performance during object selection, the most important parameters to measure are task completion time and errors found during selection (Bowman et al., 2002).

In Wingrave’s et al. (2005) study, one selection method is evaluated measuring performance by time and angular error when varying object distance. The time to select an object was increasing with an increased distance and accuracy was also positively correlating with the distance. As discussed in Wingrave’s et al. (2005) study, there is a tradeoff between speed and accuracy when measuring these parameters during object selection. It is impossible to perform optimally in both time and accuracy in the same time since it is seen as antipoles towards each other. A bivariate analysis can determine how the two parameters are correlating (Statistics How To, 2017), and the possibility of correlation between the performance measures must be taken into account when coming to conclusions.

Several selection methods can be applied on object selection. From pressing buttons, to gazing. One method, not that commonly used, is a selection triggered when users point onto an object for a certain amount of time, the so called dwell on object approach (Argelaguet et al., 2012). Negative effects caused by this selection technique is that fixation on objects could lead to unwanted selection. Also,

the time it takes for the selection to be triggered, the dwell time threshold, adds a fixed latency each selection.

METHOD To investigate how selection of objects is affected by distance and amplification an experimental study was set up with 13 participants. The aim was to measure the test subjects performance in time and accuracy when selecting an object appearing at 13 different object positions, see cubes in figure 2, within the HMD’s FOV of 100°. Three different levels of amplifications were applied onto the virtual head rotation. During the test, test subjects were sitting down in order to use less movements from the hips and legs that can displace the physical head rotation during selection of objects.

The three linear AVHR’s that were implemented into the VE had the intensity of: no amplification of physical head rotation (x1), two times amplification (x2), and three times amplification (x3). The different linear amplification strengths will be referred to as; no amplification (x1), x2 amplification and x3 amplification.

Data was collected from the 12 positions seen in figure 2, the green cubes. Due to symmetry reasons, positions of equal radial distance and the same angular distance (in absolute value) were considered identical, rendering 6 positions: angular distance ∓20° or ∓45°, and radial distance 5, 10 or 20 meters. Angular distance is measured from the 0° angle, straight in front of the user, to the angle of the first set of objects at ∓20° or to the second set of objects at ∓45°. The six object positions will further be referred to as 45°-5m, 45°-10m, 45°-20m, 20°-5m, 20°-10m and 20°-20m.

Figure 2: Illustrates the experimental set up in the virtual world. The small circle in the middle illustrates the user’s head with the HMD on. The green cubes are the objects the test subject selects at different distances and angles. The HMD’s FOV is marked with red lines.

The test subjects were told beforehand to select the objects as accurate and fast as possible. To measure the time and accuracy for each amplification and position, every other object was placed at 0°, the red cube in figure 2, forcing each selection to start at 0°. Accordingly, the time (sec) variable started when selecting object at position 0° and ended when selecting the next object appearing at some of the positions; ∓45°-5m, ∓45°-10m, ∓45°-20m, ∓20°-5m, ∓20°-10m and ∓20°-20m. The object position was randomly generated. The objects appeared on a fixed horizontal plane in front of the test subject. In turn, angular error was measured in how far away, in absolute value, the test subjects aimed from the object center when selecting it measured in angeles.

57 objects were shown for each test subject, whereof 29 were placed at angle 0° and the other 28 at some of the six positions. Of these 57 objects, 19 were carried out using a x1 AVHR, 19 with a x2 AVHR and 19 with a x3 AVHR. During the test session, the order of the amplification (x1, x2 and x3) was randomized. When changing AVHR, a new color was set on the objects popping up (red = x1, green = x2 and yellow = x3). This made it possible to ask users about perceived differences between the different AVHR settings without informing them about the specificities of the settings, and possibly affecting their replies.

As mentioned, the dwell selection method triggers a selection of an object when users look at it for a certain amount of time. In order to circumvent unintentional selection, only one object at a time is shown in the experimental setup. The fixed latency added onto the selection was 0.5 sec. This aiming to minimize the correlation and dependency between the two parameters time and accuracy. Also, a focus dot was added onto the FOV, reassuring users that they focus on an object.

A two factorial ANOVA analysis was conducted on the data set to determine the difference between amplifications; x1, x2 and x3, in accuracy and time for each position. Also, a two tailed t-test was performed with the same purpose. If the p-value of the t-test was below 0.025, or the p-value of the ANOVA below 0.05, the hypothesis: there is no difference in mean value (accuracy or time), was rejected and we were going along with the alternative hypothesis, there is a difference in mean value. This to evaluate which AVHR that was the fastest or most accurate one at each position.

The recruitment of participants was made by hiring experienced IT savvy people at the CSC department at KTH between the age of 23 and 45. Out of the 13 test subjects, there were 9 males and 4 females. Nine of them considered themselves as novice users of VR, two as moderate and two as experienced. No names, videos or voice recording were done or taken of the test subjects. Only notes during the

interviews were taken. A Homido V2 VR headset was used and the platform running the software was an Android smartphone. The test environment was developed in Unity. The test subjects had to fill in a questionnaire concerning their age, earlier usage of VR and whether they saw themselves as novice, moderate or experienced VR users. Also, a qualitative interview (see appendix A), was performed to investigate the perceived differences between the amplifications. The 13 participants will be referred to as P1-P13.

RESULT In the following section the result from the study will be presented. The positions where the amplification is significantly more accurate or faster than another amplification will be more detailed presented.

A total of 370 data points for both the time to select an object and the angular error for each selection were used in the data analysis. Because of the randomized object positions, the number of data points for each position varied, see table 1. The amount of collected data points for each position and for all test subjects, was between 15 to 29. As seen in table 1, the average time and angular error varied in small ranges between the different amplifications.

Table 1: Mean values for angular errors (AE) and time to select the object (TtC) and number of data points (DP).

T-test Analysis The two tailed t-test analysis, that was done with the aim to determine how the different amplification affected time and accuracy, showed that there were several significant

differences in average angular error and time between three of the six positions; 45°-5m, 45°-10m, 45°-20m, 20°-5m, 20°-10m and 20°-20m, see table 2 and 3. The positions showing significant results was 45°-5m, 45°-10m and 20°-10m.

Accuracy The test subjects selected the objects significantly more accurate when using the no amplification (x1) than the x2 amplification for both 20°-10m and 45°-10m, see diagram 2. For position 20°-10m, the no amplification was significantly (p = 0.001) more accurate (0.465° angular error) than the x2 amplification (0.988° angular error). Interestingly, the x3 amplification was also significantly (p = 0.004) more accurate (0.535° angular error) than the x2 amplification for this position, 20°-10m, but less accurate than the no amplification.

For position 45°-10m and similar to position 20°-10m, the no amplification (x1) was significantly (p = 0.018) more accurate (0.471° angular error) than the x2 amplification (0.855° angular error). Contrary to what was observed at position 20°-10m, the no amplification was also significantly (p = 0.006) more accurate than the x3 amplification (0.958° angular error). See table 3 and diagram 2. Time There was also significant differences measured in time when selecting objects with the different amplification levels, see table 2 and diagram 1. First, there was a significant difference in average time between the x2 amplification and x3 amplification for position 20°-10m and 45°-10m. For position 20°-10m, the x2 amplification (1.155 sec) was significantly (p = 0.002) faster than the x3 amplification (1.667 sec). For position 45°-10m the x2 amplification (1.1.347 sec) was significantly (p = 0.004) faster than the x3 amplification (1.775 sec).

Secondly, there was a significant difference in average time between the 1x (no amplification) and x3 amplification for position 20°-10m and 45°-5m, see table 2. For position 20°-10m, the no amplification (1.256 sec), was significantly (p = 0.013) faster than the x3 amplification (1.667 sec). Opposed from this result, that the x3 amplification was significantly slower than the other amplification levels, turned out being the fastest one for position 45°-5m. The x3 amplification (1.156 sec) was significantly (p = 0.001) faster than the x1, no amplification (1.525 sec) for position 45°-5m. In table 2 and 3, the result rejecting H0, no difference in mean value, is outlined with a *.

Table 2: T-test to determine whether there is a difference in average time to select an object between the different amplifications; x1 and x2, x2 and x3, and x1 and x3. As seen in table, H0 is rejected for conditions marked with *.

Table 3: T-test to determine whether there is a difference in average angular error between the different amplifications; x1 and x2, x2 and x3, and x1 and x3. As seen in table, H0 is rejected for conditions including*

Diagram 1: Average Time to Select Object per Position. The average time to catch object for three certain positions; 20°-10m, 45°-5m and 45°-10m, including all three amplification levels; x1, x2 and x3.

Diagram 2: Average Angular Error per Position. The average angular error for two positions; 20°-10m and 45°-10m, including all three amplification levels; x1, x2 and x3.

Additional ANOVA Results The complimentary ANOVA analysis, that was done on the same data set, confirmed all significant differences found in the t-test but found two additional significant differences. One at position 45°-20m, where x2 amplification (1.784 sec) was significantly (p = 0.016) faster than the x3 amplification (2.125 sec), and another significant (p = 0.005) difference in angular error at position 45°-5m, where the no amplification (1.055° angular error) was more accurate than the x3 amplification (1.591° angular error). The coinciding significant results from the t-test and ANOVA analysis can be viewed in diagram 1 and 2. Univariate Analysis According to the Univariate analysis, both the level of amplification and the position of objects had a significant (P < 0.05) influence on time and accuracy. Since the Partial Eta Squared variable was 0.043 for amplification and 0.281 for position, the position had a greater influence on the time parameter than the amplification level. Henceforth, the same test determined that the amplification level and the position of objects had a significant (P < 0.05) effect on the angular error. With the same reasoning as above, the Partial Eta Squared for angular error showed that the amplification had less influence on the angular error than the position.

Interviews From the interviews, some patterns were observed. Twelve test subjects (not P6) out of 13 noticed a difference between the different amplification levels. The general thoughts was that they perceived a difference in precision and how “fast” they could catch the objects.

The x3 amplification got mostly negative comments. Six test subjects (P5, P7, P9, P10, P12, P13) described the amplification as the most difficult one, due to the difficulties of focusing on objects and because they tended to “shoot” over the actual object. Two test subjects (P5, P13) mentioned explicitly that the x3 amplification made it more difficult to focus compared to 1x and 2x amplification. One test subject said that “the focus dot sweeped back and forth around the cube (object), which made it difficult”. No test subjects described the x3 amplification as natural. One participant (P11) perceived the x3 amplification as the fastest one. It was also described as the “very fast” one and less comfortable compared to the no amplification and x2 amplification (P2). Two test subject did not comment on the x3 amplification (P3, P4).

The x2 amplification was the one that received most positive comments out of the different levels of amplification. Three test subjects (P8, P9, P10) described this amplification as the most easy one to catch the objects with. One test subject (P10) described it as the most moderate one out of the three amplification levels. Four test

subjects (P3, P4, P5, P9) described the x2 amplification as the most natural one. One test subjects (P10) thought they performed faster with the x2 amplification compared to no amplification and x3 amplification. One test subject (P13) said that the x2 amplification was “the best one” but could be perceived as a bit too fast.

Interestingly, the AVHR with no amplification received negative comments from five of the test subjects (P1, P5, P9, P10, P13). All of them experienced this AVHR as slow. One test subject (P9) thought the AVHR (x1) was the most difficult one and felt “uncomfortable” when selecting objects. However, seven participants (P2, P7, P8, P10, P11, P12, P13) experienced the x1 amplification as the most natural one and one test subject (P2) thought that they selected the objects faster with this amplification. One test subject (P1) said, “the red objects(no amplification) felt best but I felt slow”. Another test subject (P13) reflected upon the color red, as all x1 amplification objects were, could be perceived as negative.

The order of which the different amplification levels was presented in for the test subject seemed to have some influence on their perception of the different amplification levels. All test subject except from one (P10), that perceived no amplification (x1) as slow, had a higher amplification, x2 or x3, applied as an AVHR before the no amplification (x1). For six participants (P2, P3, P4, P5, P11, P13), the user test started with the x2 amplification. Since this amplification got only positive comments, this might have influenced their perception of the amplification. As mentioned, one of the test subjects (P6) did not notice any difference between the amplifications, and in this case the amplification was growing from x1 to x2 to x3. In the same time there was other test subjects having the same order of amplifications and did notice a difference in “speed”. Even the x3 amplification was applied first or last in order, the test subjects responded similar, as “too fast”.

DISCUSSION In the following sections the result of performance for object selection, in terms of speed and accuracy, under varying distances and amplifications will be discussed.

The interesting result from the Univariate analysis was that the object position had a greater influence on accuracy and time, than the amplification level. One explanation to this could be that the different distances gave rise to a variation in object sizes. At a larger distance the visual appearance of object becomes smaller and vice versa. This is also discussed in Poupyrev et al., (1998) and Wingrave’s et al., (2005) studies but in these cases, a greater size of an object, objects closer to the user, correlates to faster object selection. The visual object size could be one explanation to why there was no significant difference in accuracy in 20 meters. The visual size of the object at 20 meters was so small that the difference in angular error also became

insignificantly small.

According to the t-test, no amplification (x1) was more accurate than other levels of amplifications. For the position 20°-10m, both the no amplification and the x3 amplification were significantly more precise than the x2 amplification. Why the x3 amplification was generating such a significant precis result compared to the x2 amplification in this position is hard to find an explanation for. The 20°-10m being the closest position, measured in angular distance, might be one suggestible explanation, since the close distance and large visual size of object simplified fine tuning of object selection.

Why there was no significant result in accuracy from the t-test at a distance of 5 and 20 meters could also potentially be explained by the visual size of the objects. In the case of 5 meters, the object had a larger visual size in comparison to the objects at 10 and 20 meters distance, which made the angles during selection vary more while still hitting the target, resulting in a greater variance. On the other hand, the visual size made it easier to select the objects, which could could be one explanation to why the x3 was faster than the other amplification levels for 5 meters when measuring time. Worth mentioning is that the ANOVA analysis alone, did indicate that the no amplification (x1) was significantly faster than the other amplification levels at position 45°-5m. Since the t-test did not showing this as a significant result, the credibility of the result is questioned.

According to the t-test, the x2 amplification was overall significantly faster than the other levels of amplifications for object selection at position 20°-10m and 45°-10m. In the ANOVA analysis, an additional position, 45°-20m, gave a significant result confirming that even at this distance the x2 amplification was much faster than the other amplification levels. This result showing that the x2 amplification is the fastest one during object selection, corresponds with results in previous study (Jay et al., 2003). However, the result of position 45°-20m did not appear in the t-test but only in the ANOVA analysis, the credibility for this specific result is weaken. One explanation to why the x2 amplification was the overall fastest amplification level is probably because of it being fast, but not too fast to generate problems with fine tuning during selection.

The x2 amplification received only positive comments during the interviews. Since the x2 amplification was the amplification level in between the no amplification and the x3 amplification, the amplification could easily be perceived as the most moderate one in relation to the other amplification levels. Moreover, the perception of both the no amplification (x1) and the x2 amplification could also been affected by the dislike many test subjects had for the x3 amplification. Relative to the x3 amplification both x2 and the no amplification was perceived as better. Another

explanation to why there was such a positivity towards the x2 amplification could be explained by the order of amplification levels which the test subjects were exposed to. Although the amplification levels were randomly ordered, it is difficult to get rid of the effect that the order has on the user perception. Therefore, some of the positive comments about the x2 amplification could possibly been influenced by the x1 and x3 amplification and exposure procedure of amplification levels towards the test subjects.

Both the x1 and x3 amplification got negative comments from test subjects. The no amplification (x1) was the most accurate one according to the quantitative data, but got many comments from the interviews, indicated that it was received as slow. Four out of the five test subject perceiving the no amplification as slow, was exposed to this amplification right after being exposed for the x2 or the x3 amplification. Therefore, the perception of the no amplification of being slow, seemed to be affected by the order of the amplification levels. In turn, the user perception of the x3 amplification seemed to be less influenced by the order, since no relation between order and perception of amplification could be seen from the interviews. So, the perception of the no amplification could be more influenced by the order of amplification levels than the x3 amplification was when it comes to users perception of the different amplification levels.

Since the no amplification was generally the most accurate one and the x2 amplification generally the fastest one, the optimal amplification would intuitively be somewhere in between these two amplification levels. So in a future study, there would be interesting to do a similar user study but where the x3 amplification is replaced with a x1.5 amplification. That could potentially generate interesting result and give more detailed insights in how a optimal AVHR should be designed to favour object selection in different distances. An optimal amplification for object selection should both be as fast and accurate as possible.

In retrospective, it could have given more equity to the study if each test subject was exposed for only one single amplification level and only reflected upon that one or if having a short pause between each amplification level to make the difference between them less obvious for the test subject. Hopefully, the test subject’s perception of the different amplification levels could become less influenced by its order. To reduce the effect from the object's visual size a dot in the center of each cube, which remained size independent of the distance, could have made it easier for the test subjects knowing what to aim for and focus on during selection. Also, the distance of 20 meters could be exchanged by a distance of 15 meters, to minimize the effect of visual object size.

CONCLUSION The aim of this study was to look at how different amplification levels affect object selection for objects placed at varying distances. Overall, users perceived the no amplification as natural but slow and the x2 amplification as both natural and fast, while the x3 amplification was generally perceived as too fast and difficult to focus with on objects at all distances. In terms of the time needed for selecting objects, x2 amplification was the fastest for both 10 and 20 meters, while 3x was faster for 5m. The reason behind x3 performing better on closer distances is probably because of the larger visual size of closer objects in the experiment, which required less accuracy for selection. In terms of accuracy, the no amplification (x1) was the most accurate one for the distances of 5 and 10 meters. Why no significant result in accuracy could be seen at 20 meters distance, is probably an effect of small visual size of the object. The small visual size at this distance required an accurate selection to be able to select the object for all amplification levels.

In conclusion, the x2 amplification appeared to be an effective choice for AVHR based on its fast response and user preferences. However, this study only investigates x2 amplification compared to no amplification and x3 amplification, meaning x2 amplification might not be the optimal choice for AVHR, but rather an amplification level in its proximity. Therefore a study investigating amplification levels near the x2 amplification would be interesting in order to get an even better understanding of which level of amplification that is the most effective and accurate choice of AVHR for object selection in different distances.

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APPENDIX A - INTERVIEW QUESTIONS

Did you notice any difference between the different colors on the objects?

● If yes, how would you describe the differences? ● Were any of the colors perceived as more or less natural?