- This article investigates how people perceive distances in virtual reality (VR) and use that information to execute a representation of a real life throwing motion. In order to measure accuracy, this research proposes a throwing motion testing framework, which acquires metrics data from both the real and virtual environments. The results show, that the examinees tend to throw more accurately at longer distances and use excessive amounts of force.
During the last decade virtual reality technology has significantly improved and is used in different technological spheres. The visual representation is becoming more realistic and looks more natural. Although technology is evolving, it is hard to replicate human senses. Therefore, this study tries to analyze how accurately people perceive virtual world distances when executing a throw.
This study presents a throwing motion testing framework to determine the differences between the virtual and real world’s environment perception capabilities. It will discuss similar studies in the field related to perception and motion tracking, explain the testing framework and methodology, the experiment’s process, discussion about the results and drawbacks of this study and the conclusion, possible future.
A similar project [
Another article checked people’s ability to locate
themselves in a virtual environment. Their task was to point
at themselves in a VR platform using a pointer. The
experiments results stated that participants most commonly
locate themselves at the upper region of their face and that
draws a conclusion that people in a virtual environment are
more head-centered. [
A more recent study [
A similar study to research [
The study [
As mentioned a few times in other researches people tend
to underestimate distances in virtual reality and according to
Steven M. LaValle, the cause for that could be different gaps
between pupils [
II. THROWING MOTION TESTING FRAMEWORK
To determine the differences in perception between reality and a virtual environment, we focused on the different aspects of throwing kinematics in reality and VR. Three main characteristics are taken into consideration: throwing distance in reality, throwing distance in virtual reality and the initial velocity of the hand tracker in a throwing motion.
To measure the above mentioned features a throwing simulation framework was created. During the testing procedure participants throw a 10 gram ball to three different distances (2 meters, 3 meters, 4 meters) and a tracker attached to their hand transmits VR data which is recorded digitally, while real life distance is measured with a ruler. Each participant has three attempts at three distances with the virtual reality headset being used and another with it mounted on top of their head for tracking accuracy.
The testing system is developed using Unity Engine and HTC Vive Pro VR headset and tracker. The framework’s visual environment is a replica of the room where the simulation was performed so it would not cause distractions to the participants. Distances at which the ball is thrown and standing position are marked in both the real and virtual environments (Fig. 1 and Fig. 2).
In the experiment, HTC Vive Pro virtual reality headset and tracker are both connected to a personal computer with Windows 10 operating system. The tracker’s data collecting Base stations 2.0 were placed at 5 meter distances from each other, at opposing corners of the room. The testing framework was built in Unity 2018.3.5.f1 with an implemented SteamVR plugin. The original plugin’s view for the ball throw scene was edited so that it would replicate the experiment room and the stock throw function was modified so that it didn’t require any buttons to be pushed. The throw in the system is initiated when the tracker is swung and the velocity of the tracker starts to slow down after the constant increase in velocity at the start of the throw. The simulated environment replica consists of a 9 meter by 6 meter square room with an open top. The layout is positioned at the exact locations of real world objects.
To collect quite accurate motion data the tracker is attached to the palm of the participant and the ball is put on top of the device (Fig. 3). When the person executes a throw the tracker captures the initial velocity, and upon slowing down the system initiates a throw in virtual reality and sends the collected speed and data about the ball’s collision with a ground surface to a text file. The real distance is measured with a ruler and all collected digital and non-digital data is saved in a spreadsheet.
The main goal of the experiment is to determine how accurate is a human’s perception at determining distances using a virtual throwing mechanism compared to a real world throw.
The experiment participants were six people: 4 males and 2 females. The participants age ranged from 19 to 25 years (mean age 22.3), all of them were healthy and didn’t suffer from VR sickness. At the beginning of the test, the participants were given time to practice throwing in virtual reality and get used to it. Then the examinees did three consecutive throws at specified distances without a headset and then they had three attempts with the virtual reality device. This process was repeated three times at three different shooting distances. During the experiment, participants were not allowed to move from the starting position. The collected distance and velocity data was saved in a spreadsheet.
The experiment’s results are presented in Table I where every user’s average thrown distance is shown in a centimeters format. Results of shots with virtual reality equipment and without it are separated and the total average of each baseline distance is calculated.
From Table I it is easy to see that people throw the ball most accurately at a distance of 3 or 4 meters when using the VR headset, whereas at the 2 meter mark there is a 10 centimeters deviation. However, with unobstructed vision people throw the ball more accurately at the first and third distances and in this case there is about a 10 centimeters deviation from the second distance. This data shows that with an increase in distance people’s throws tend to become more accurate, whereas near distances are more difficult to judge. b. SD – Standard deviation In addition, from the bar chart shown in Fig. 4, which represents the average miss distance from a mark (negative value if it is shorter than the baseline distance and positive if the average value is greater), it is noticeable that the experiment participants tend to underestimate distances and throw the ball at a shorter distance. Only two columns show a slight ball overthrow and both belong to results achieved in virtual reality .
Table II shows every participant’s standard deviation of three throws and average standard deviation which is about 17 centimeters. Therefore, it can be said that the experiment needs an increase in participants and throw attempts to make the experiment’s data even more accurate.
Data about the average initial velocity is presented in a clustered columns chart and a scatter graph (Fig. 5 and Fig. 6) where the baseline distances and different environments are separated. Besides average values, medians are given to make the data more accurate.
From Figures 5 and 6 it is noticeable that people tend to throw the ball with more power when they are in a virtual environment than when they are in the real world. This statement also is reaffirmed by the medians of all throws in real and virtual worlds.
This study was conducted to find out how accurately people perceive the virtual environment and decide what amount of power is needed to throw the ball. To achieve this goal 6 participants took part in the experiment where they had to throw a ball at 3 distances with and without a VR headset.
After all tests, the collected data shows that people’s
accuracy with VR tends to increase with an increase in
distance and that the average initial speed tends to be higher
than pitching the ball without the headset. To explain the
increase in velocity we could say that because people are
more head-centered [
These results show, that the described method can be
used to calibrate hand strength in Virtual Environment fields,
such as gaming [
To acquire more accurate estimations we cannot forget that all velocity data is collected by a wireless tracker and the real ball that was put on the tracker could interfere with results and that could be a reason why the standard deviation for a few participant’s throws was so high.
In addition, to help the person better comprehend the
depth of a virtual world during the experiment it could be
allowed for the participants to walk around the room as
shown in research [
Furthermore, it was brought to the examinees attention, that to get more accurate results the participants had to do a bigger backswing while performing the throwing motion to get a more consistent velocity and more suitable throw initialization timings.
In this study, we concluded, that people perceives 2 – 4 meter distances nearly the same as in real life. Moreover, people tend to use 3 to 5 % more power when throwing a ball in virtual reality than in real life. However, the used methodology needs improvement (some throws standard deviation is as high as 45 centimeters) to eliminate unnecessary factors, such as inaccuracy of manual real world measurements and signal integrity loss from ball position relative to the sensor. Furthermore, a larger pool of participants is needed to achieve precise data averages and calculations. There is also the possibility to attach a separate sensor to the ball that is being thrown by the participants, thus eliminating the need for real world measurements by allowing us to compare the data between both throws directly. Although the research is not perfect it has considerable potential to be used as a calibration tool for various virtual reality fields which involve hand motion and arm strength.