A study on the effects of the gravity and the visually-perceived subjective vertical on occurrence of visually-induced motion sickness caused by 3D movie

研究了3D电影产生的虚拟空间中的自我运动感和特殊定向感对视觉诱发晕动病发生的影响。当3D电影提供虚拟现实时，垂直方向的感觉，即主观垂直，是通过视觉感知来获得的。由虚拟摄像机在具有/没有上下方向的虚拟空间中拍摄的3D电影是由计算机图形学制作的，因此主观垂直在其中一些人中可以在视觉上感受到，而在另一些人中则不是。他们被用来比较视觉诱导的晕动病的严重程度。在向上和向下方向(视觉垂直保持在恒定方向)的虚拟空间中围绕垂直轴旋转引起的不适程度与在没有向上和向下方向(视觉垂直没有被感知)的虚拟空间中的旋转相似。在具有上下方向的虚拟空间中围绕水平轴旋转(视觉垂直保持旋转)引起的不适感比以上两种旋转更严重。自我旋转相对于重力的方向改变的感觉可能增强了不适感，因为它除了产生视管冲突外，还产生了视觉-耳石感觉冲突。此外，还研究了虚拟空间中的现场感对视觉诱发运动病发生的影响。两个摄像机安装在一个两轴旋转器上，通过改变摄像机的视角在真实空间拍摄3D电影。3D电影被投影到屏幕上，观众可以改变视角。随着观众视角的增大，临场感增强，自我运动感增强，视觉诱发晕动病的严重程度增强。根据摄像机视角的不同，上述感觉或不适的严重程度没有显著差异。

The effects of the sensation of self-motion and special orientation in a virtual space generated by 3D movie were investigated on occurrence of visually-induced motion sickness. When virtual reality is provided by 3D movie, the sensation of the vertical direction, subjective vertical, is derived via visual perception. 3D movies, taken by virtual cameras in virtual spaces with/without up-and-down direction, were produced, by computer graphics, so that the subjective vertical was visually perceived in some of them, and was not in others. They were used to compare the severity of visually-induced motion sickness. Rotation around the vertical axis in a virtual space with up-and-down direction (the visual vertical kept in a constant direction) caused a similar degree of discomfort, compared with rotation in a virtual space without up-and-down direction (the visual vertical was not perceived). Rotation around the horizontal axis in a virtual space with up-and-down direction (the visual vertical kept rotating) provoked severer discomfort than the above two rotations. It is likely that the sensation of self-rotation with directional change relative to the gravity enhanced the discomfort because it generated visual-otolithic conflict of sensation in addition to visual-canal conflict.The effects of the sense of presence in a virtual space were also investigated on occurrence of visually-induced motion sickness. Two video cameras were mounted on a two-axes rotator and took 3D movies in a real space with changing a view angle from the cameras. The 3D movies were projected on a screen with changing a view angle from audiences. In accordance with enlargement of the view angle from audiences, the sensation of presence increased, the sensation of self-motion became more intense, and the severity of visually-induced motion sickness enhanced. There found no significant differences in the above sensations or the severity of discomfort depending on the view angle from cameras.