How to improve the sensation of distance when interacting
with objects in VR game
Nak Hyeon Ku, Young Jick Jang, Tae Soo Yun
Department of Visual Contents
Graduate school, Dongseo University
Busan, South Korea
firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
To reduce the sensation of error in the distance that occurs when interacting with objects in virtual reality (VR) games, I propose in this paper, a way to improve by two methods, the blur effect and the enlargement and reduction of the image. VR games with HMD provide users with a visually intense immersion experience. However, since there are many differences between the real world seen directly by the human eye and the virtual space seen on the screen, the user feels an error in the distance with the contents of VR, which leads to the reduction of the feeling of immersion that is the advantage of the VR game. As a result of the usability evaluation of my own VR game using the method presented in this paper, it can be confirmed that the sensation of error in the distance perceived by the user is less than that of the conventional one.
Keywords- VR;Interaction;Usability Evaluation;
The VR game provides a strong visual stimulus and makes the participants feel immersed in the VR game. However, in the VR game, there is a difference between what is perceived by the human eye and the reality, which causes an error in the sensation of the distance and interrupts the interaction with the object in the virtual space. This greatly reduces the user's feeling of immersion in the content, which causes the dissatisfaction of the VR game. In this paper, I propose two methods to improve the sensation of error in the distance. First, the blur effect and second, image enlargement and reduction. In this paper, I applied these methods to the VR game I made and verified the usability by a comparative evaluation. I consider that this will be the cornerstone of future research.
2. Sense of distance in virtual space
There are several limitations in the VR environment compared to the perception of the real space by the real eye. "In VR, the image screen is fixed, so it is impossible to recognize it as when moving the real eye of a human being and the display resolution of the HMD is limited to the limits of the hardware and the viewing angle is also inferior to the real eye. " These differences and limitations are applied in a complex way, so that the participants feel as if the object is closer in the virtual space compared to the real distance, and an error occurs in the sensation of the distance.
3. How to improve the error of distance sensation
In accordance with the order of investigation, I will first investigate the factors that affect the recognition of distance through preliminary studies. Then, I will come up with two ways to solve this. These ways will be implemented and applied to VR game based on Unity3D. And, finally, to verify the validity of the study results, I will conduct a comparative evaluation of usability and the results will be reviewed.
Fig. 1 Image using blur effect
Preliminary studies have shown that the two methods of blur effect and enlargement and reduction of images can affect the perception of distance in a person. First, the blur effect, which is shown on the left side of Figure 1, is used by film makers working with a miniature image model to make it look like a real size in a movie scene through a small camera aperture. On the other hand, the right side of Figure 1 shows the tilt-shift effect that allows a real-sized object to appear as a miniature model. As we saw, the "Blur effect plays an important role in the transmission of the desired size and distance. " Secondly, the enlargement and reduction of images can enlarge or reduce the size of the image displayed on the right and left sides of the HMD to affect the binocular disparity and thus control the sense of distance.  To implement these two methods in Unity3D, I used the Gaussian filter shown on the left side of Figure 2. The g (x, y) is the size of the Blur filter calculated by the Gaussian function, and it adjusted by the Σ value. (x ', y') means the size of the image enlarged or reduced by the s value magnification.
Fig. 2 Gaussian filter to implement the Blur effect (left) Equation for conversion to enlarge and reduce images (right)
These two methods are applied to Treasure Hunter, a VR game created by myself with Unity3D. Treasure Hunter is a VR adventure game that escapes from an Egyptian pyramid by acquiring established items.
4. Experimental Methods and Results
The following experiment was conducted to verify the effectiveness of Blur effect and enlargement and reduction of images to improve the distance sense error of VR environment.
4.1. Experimental Methods
As the experiment method, the comparative evaluation of usability was used. I compare the VR game adventure, Treasure Hunter, dividing it before the application (Table 1, Before) and after the application (Table 1, After) of the two methods proposed. The experiment consisted of 10 people and the average age is 24 years old. First, 10 participants were asked to experience it before the application, and then, using the 5-point scale, they measured the degree of error in the distance by checking the items, 5 means a very significant error and 0 no error, then I obtained the average of these values. Then let the 10 participants experience again the game after the application to check the feeling of error in the distance for obtaining the average value. Finally, compare the two average values derived.
4.2. Results of Experiment
In Table 1, the Before is a scene before the application of the method of improving the sense of distance, and the After is a scene in which the two methods of Blur effect and image enlargement and reduction, are applied. A is the blur effect applied only to a specific object in order to adjust the distance to the object. B shows that the image size value is reduced to Before in Table 1.
Table. 1 Result image and Result of comparative evaluation of usability
According to the result of the experiment, the participants perceived the sensation of error in the distance of a value of 4.1 before the application of the two methods in the VR game. On the other hand, the sensation of error in the distance of the VR game after the application of the two methods was perceived as 2.6. It was confirmed that the value decreased by 1.5 compared to the state prior to the application. To summarize, it can be said that it is the same as the Figure 3 below.
Fig. 3 Result of Usability Evaluation
I verified that the sensation of error in the distance is alleviated through the usability evaluation of the VR game which is made by applying the two methods presented in this study. This provides the user with greater interactivity with the realistic objects than the existing ones, so that the user can feel a greater degree of immersion for the VR game, thereby achieving a high degree of perfection. As a follow-up study, I will investigate the factors that can enhance the interactivity of VR games as well as improve the sense of distance, and apply them to VR games for more improvements.
 Messing, Ross, and F. H. Durgin. "Distance perception and cues to distance in virtual reality." ACM SIGGRAPH Symposium on Applied Perception in Graphics and Visualization, 2004
 ROBERT T. HELD, EMILY A. COOPER, JAMES F. O’BRIEN, and MARTIN S. BANKS,“Using Blur to Affect Perceived Distance and Size”, ACM Trans Graph, Mar, 2010.
 Zhang, Ruimin, et al. "Minification affects verbal-and action-based distance judgments differently in head-mounted displays." ACM Transactions on Applied Perception (TAP) 9.3 (2012): 14