No abstract

Viewing a scene on a screen display differs greatly from viewing it in the real world. The visual information is conveyed via a flat screen at a fixed distance, and this screen distance can influence how viewers perceive depth in stereograms in conventional stereoscopic displays. This study investigated whether screen distance influences perceived depth in Virtual Reality (VR) systems providing additional motion parallax information. Participants adjusted the depth of a vertical dihedron displayed as a random-dot stereogram. In a first experiment, the stimulus was presented either alone in a gray untextured background or in a cue-rich environment. We found that despite the extra motion parallax information in VR systems compared to conventional stereo-displays, physical screen distance still affected depth perception substantially at longer simulated distances. However, the effect lessened when observers were immersed in a rich and structured environment, possibly allowing them to use other depth cues. A second experiment assessed the influence of potentially potent display-related factors (resolution, display orientation, luminance non-uniformity, and specular reflection), as well as the effect of accommodation-vergence (A-V) conflict size. Depth perception was compared between a Head-Mounted Display (HMD) and an L-shaped system, and between a CAVE and an L-shaped system. These comparisons between CAVE-like VR systems and HMDs revealed that A-V conflict and inclusion of a rich environment were the major factors impacting depth perception. These results have practical and methodological implications for the reliable use of VR systems, especially where accurate depth-matching is involved.

The creation of man-made shapes can be seen as the exploration of designers' 'Mental Shape Space', often supported by design reviews. To improve communication among the designers during these reviews, we introduce a new physicallybased method to intuitively deform man-made shapes. This method is based on as-rigid-as possible (ARAP) shape deformation methods, known to offer a direct surface manipulation and to generate visually pleasant shapes by minimizing local deviations from rigidity. However, the organic character of ARAP shape deformations leads to undesired effects, such as surface collapsing or bulging because of an inappropriate stiffness model over the object. In this paper, we first link the designers' needs to ARAP handle-based variational mesh deformation processes. Then, we study and characterize the ARAP energy and its variants from a structural mechanics point of view. Our insight is that controlling the material stiffness could prevent the undesirable organic effects. Yet, we shed light on the fact that none of the ARAP-based methods offers an appropriate stiffness distribution over the object from a mechanical standpoint. We do so by introducing an appropriate anisotropic material, called orthotropic material, to improve the stiffness distribution over the surface and its deformation behavior for man-made shapes. This material is associated with a membrane-like structural behavior to further improve the stiffness distribution. Thanks to these settings, we derive a robust and intuitive deformation process that produces an anisotropic mesh deformation based on new edge weights in the ARAP formulation. The benefits of our new method are finally illustrated by typical design examples from the automotive industry and other man-made shapes.