Institute of Computer Science, University of Münster, Einsteinstrasse 62, 48149, Münster, Germany.
IEEE Trans Vis Comput Graph. 2011 Jul;17(7):888-99. doi: 10.1109/TVCG.2010.248.
The display units integrated in today's head-mounted displays (HMDs) provide only a limited field of view (FOV) to the virtual world. In order to present an undistorted view to the virtual environment (VE), the perspective projection used to render the VE has to be adjusted to the limitations caused by the HMD characteristics. In particular, the geometric field of view (GFOV), which defines the virtual aperture angle used for rendering of the 3D scene, is set up according to the display field of view (DFOV). A discrepancy between these two fields of view distorts the geometry of the VE in a way that either minifies or magnifies the imagery displayed to the user. It has been shown that this distortion has the potential to affect a user's perception of the virtual space, sense of presence, and performance on visual search tasks. In this paper, we analyze the user's perception of a VE displayed in a HMD, which is rendered with different GFOVs. We introduce a psychophysical calibration method to determine the HMD's actual field of view, which may vary from the nominal values specified by the manufacturer. Furthermore, we conducted two experiments to identify perspective projections for HMDs, which are identified as natural by subjects--even if these perspectives deviate from the perspectives that are inherently defined by the DFOV. In the first experiment, subjects had to adjust the GFOV for a rendered virtual laboratory such that their perception of the virtual replica matched the perception of the real laboratory, which they saw before the virtual one. In the second experiment, we displayed the same virtual laboratory, but restricted the viewing condition in the real world to simulate the limited viewing condition in a HMD environment. We found that subjects evaluate a GFOV as natural when it is larger than the actual DFOV of the HMD--in some cases up to 50 percent--even when subjects viewed the real space with a limited field of view.
如今的头戴式显示器（HMD）集成的显示单元为虚拟世界提供的视野非常有限。为了向虚拟环境（VE）呈现无失真的视图，用于渲染 VE 的透视投影必须根据 HMD 特性进行调整。特别是，用于渲染 3D 场景的几何视场（GFOV）是根据显示视场（DFOV）设置的。这两个视场之间的差异会以缩小或放大用户所显示的图像的方式扭曲 VE 的几何形状。已经表明，这种失真有可能影响用户对虚拟空间的感知、存在感和视觉搜索任务的表现。在本文中，我们分析了用户对在 HMD 中显示的 VE 的感知，该 HMD 使用不同的 GFOV 进行渲染。我们引入了一种心理物理校准方法来确定 HMD 的实际视场，该视场可能与制造商指定的标称值有所不同。此外，我们进行了两项实验来确定 HMD 的透视投影，即使这些透视投影偏离了 DFOV 固有定义的透视投影，这些透视投影也被认为是自然的。在第一项实验中，被试必须调整渲染的虚拟实验室的 GFOV，使得他们对虚拟复制品的感知与他们在看到虚拟实验室之前看到的真实实验室的感知相匹配。在第二项实验中，我们显示了相同的虚拟实验室，但在现实世界中限制了观察条件，以模拟 HMD 环境中的有限观察条件。我们发现，当 GFOV 大于 HMD 的实际 DFOV 时——在某些情况下高达 50%——即使被试在有限的视野下观察真实空间，被试也会将 GFOV 评估为自然。
