Abstract
Users sometimes lost their balance or even fell down when they played virtual reality (VR) games or projects. This may be attributed to degree of content, high-rate of latency, coordination of various sensory inputs, and others. The authors investigated the effect of sudden visual perturbations on human balance in VR environment. This research used the latest VR head mounted display to present visual perturbations to disturb balance. To quantify balance, measured by double-support and single-support stance, the authors measured the subject's center of pressure (COP) using a force plate. The results indicated that visual perturbations presented in virtual reality disrupted balance control in the single support condition but not in the double support condition. Results from this study can be applied to clinical research on balance and VR environment design.
TopIntroduction
People live in the three-dimensional (3D) physical world and traditional two-dimensional (2D) flat images such as photo or video are lack of the third dimension information (Geng, 2014). Almost half of human brain capacity is devoted to process visual information and the limitation of flat images and 2D displays will limit human’s ability to understand the complexity of real-world objects (Geng, 2014). On the other hand, 3D display technologies improve perception and interaction with 3D scenes, and hence can make applications more effective and efficient (Mehrabi et al., 2013). Driven by the rapid improvement of computer technology, 3D display has become more powerful, affordable and comfortable. One of the 3D displays that widely adopted is stereoscopic display. Stereoscopic is recognized as one of the oldest 3D display systems and it was first proposed by C. Wheatstone in 1838. This type of display was based on stereopsis, where an observer’s left and right eyes receive different perspectives separated by a stereoscopic device that the observer is wearing (Nam Kim et al., 2013). One of the stereoscopic displays is anaglyph (Image 1a in Figure 1) that use two color filtered images and glasses that usually utilize red-cyan, red-green, green-magenta and magenta-cyan colors. The other is LC shutter system or also known as active-shutter system (Image 1b in Figure 1). It is defined as a stereoscopic technique that sends the left image to the left eye while the right eye’s view is blocked by the display device and user glasses, then presents the right image to the right eye while the left eye’s view is blocked (Turner & Hellbaum, 1986). Stereoscopic display can also use a polarized 3D system (Image 1c in Figure 1), a technique that send polarized images to the corresponding eyes through polarization glasses (Nam Kim et al., 2013).
Key Terms in this Chapter
Head Mounted Display: A display that is more or less rigidly attached to the head.
Center of Pressure (COP): The point on the force plate where the net ground reaction forces act or the point of application of the ground reaction force vector.
Torque: The rotational effect due to a force.
Human Balance: Maintaining the center of gravity within the base of support.
Single Support: Balancing on one foot with the other in the air.
Visual Perturbations: A sudden change in the visual field.
Center of Gravity (CoG): The vertical projection of the COM onto the floor.
Double Support: Standing with both feet on the ground.
Immersive Technology: Technology that blurs the line between the physical world and digital or simulated world, thereby creating a sense of immersion.
Virtual Reality: A computer-generated digital environment that can be experienced and interacted with as if that environment was a real.
Center of Mass (COM): The net location of all mass represented in 3D space.
Force: A push or a pull on an object.