Visual perception of perspective distortions

Virtual environments (VEs) provide sophisticated means to render a virtual three-dimensional space to a two-dimensional display surface by applying planar geometric projections. Iiron a realistic viewing condition the perspective applied for rendering should account for the observer´s viewpoint relative to the image. As a result, an observer may not be able to distinguish between a rendering of a VE on a computer screen and a view “through” the screen at an identical real-world scene. Little effort has been made to identify perspective projections which cause human observers to judge them to be realistic. In this paper we analyze observers´ awareness of perspective distortions of virtual objects displayed on a monoscopic computer screen. These distortions warp the virtual object and make it differ significantly from how the object would look in reality. We describe psychophysical experiments that explore the subject´s ability to discriminate between different perspective projections and identify projections that most closely match an equivalent real scene. Our results confirm that the field of view used for perspective rendering should match the actual visual angle of the display to provide users with a realistic view. However, we found that slight changes of the field of view in the range of 10-20% for our test environment did not cause a distorted mental image of the observed scene.