Perception and Mental Rotation of 3D-Freeform Surfaces in an Immersive Projection System

Abstract

This paper reports on three experiments performed to examine the effects of different visualization techniques of 3D computer-generated freeform surfaces on subjects perceptual and cognitive performance while doing CADrelated activities in an immersive VR system. Experimental perceptual and cognitive tasks included depth size estimation of a single 3D object (exp. 1), estimation of depth differences between two 3D objects (exp. 2) and mental rotation of 3D objects (exp. 3). Dependent variables were accuracy (exp. 1, 2 and 3) and response time (exp. 3). The visualization techniques we investigated were presence versus absence of binocular disparity, four different types of graphic image (wireframe, flat shading, Gouraud shading and Gouraud shading with surface normals) and two levels of shape complexity. Results showed a positive effect of binocular disparity on perceptual performance (esp. 1), in particular when concave 3D shapes were used as stimuli (esp. 2), but a limited positive effect of stereopsis on mental rotation. Furthermore, results indicated that subjects were faster in mentally rotating 3D shapes rendered with more realistic techniques, whereas perceptual estimates were found more accurate and easier when observers were presented with less realistic rendered surfaces (exp. 1-2).