Visual consistency in rotational manipulation tasks in sheared-perceived virtual environments

Sharing one large screen projection display, such as the Virtual Workbench, with multiple users can cause distortions in viewing and interaction, as the users perceive a sheared and moving space. Generally, object rotation in non-orthogonal, sheared coordinate spaces is something that should be avoided as it consequently invalidates homogeneous geometric object transformations. Although this problem seems to be artificial, in shared multiple-user VR this issue gets a real, substantial flavor. It is typically a problem for the "secondary" users viewing and interacting with a VR system. Due to rendering the scene from a different viewpoint, they perceive several distortions in the stereo image, one of which is that the VE appears to be sheared. This is also the case in our affordable approach to a multiple user VR Workbench. In this paper we describe technical aspects of our novel viewpoint compensation method to make the object selection, translation, and rotation consistent with the (secondary) user's view of the scene. We focus on description of object rotation inside sheared VE's. We demonstrate that our techniques ensure a sense of interaction consistency despite the view distortions.