In virtual reality, stereo graphics is a very common way of increasing the level of perceptual realism in the visual part of the experience. However, stereo graphics comes at cost, both in technical terms and from a user perspective. In this paper, we present the preliminary results of an experiment to see if stereo makes any quantifiable, statistically significant difference in the ability to avoid collisions with virtual obstacles while navigating a 3-D space under constant acceleration. Our results indicate that for this particular application scenario, stereo does provide a significant benefit in terms of the amount of time that participants were able to avoid obstacles.

Visual exploration of clouds of data points is an important application of virtual environments. The common goal of this activity is to use the strengths of human perception to identify interesting structures in data, which are often not detected using traditional, computational analysis methods. In this article, we seek to identify some of the parameters that affect how well structures in visualized data clouds can be identified by a human observer. Two of the primary factors tested are the volumetric densities of the visualized structures and the presence/absence of clutter around the displayed structures. Furthermore, we introduce a new approach to glyph visualization—constant visual angle (CVA) glyphs—which has the potential to mitigate the effect of clutter at the cost of dispensing with the common real-world depth cue of relative size. In a controlled experiment where test subjects had to locate and select visualized structures in an immersive virtual environment, we identified several significant results. One result is that CVA glyphs ease perception of structures in cluttered environments while not deteriorating it when clutter is absent. Another is the existence of threshold densities, above which perception of structures becomes easier and more precise.

When viewing 3-D scatterplots in immersive virtual environments, one commonly encountered problem is the presence of clutter, which obscures the view of any structures of interest in the visualization. In order to solve this problem, we propose to render the 3-D glyphs such that they always cover the the same amount of screen space. For perceptual reasons, we call this approach constant visual angle glyphs, or CVA glyphs. The use of CVA glyphs implies some desirable perceptual consequences, which have not been previously described or discussed in existing literature: CVA glyphs not only have the prospect of dealing with clutter, but also the prospect of allowing for a better perception of the continuous shapes of structures in 3-D scatterplots. In a formal user evaluation of CVA glyphs, the results indicate that such glyphs do allow for better perception of shapes in 3-D scatterplots compared to regular perspective glyphs, especially when a large amount of clutter is present. Furthermore, our evaluation revealed that perception of structures in 3-D scatterplots is significantly affected by the volumetric density of the glyphs in the plot.

The task of multiple object selection (MOS) in immersive virtual environments is important and still largely unexplored. The difficulty of efficient MOS increases with the number of objects to be selected. E.g. in small-scale MOS, only a few objects need to be simultaneously selected. This may be accomplished by serializing existing single-object selection techniques. In this paper, we explore various MOS tools for large-scale MOS. That is, when the number of objects to be selected are counted in hundreds, or even thousands. This makes serialization of single-object techniques prohibitively time consuming. Instead, we have implemented and tested two of the existing approaches to 3-D MOS, a brush and a lasso, as well as a new technique, a magic wand, which automatically selects objects based on local proximity to other objects. In a formal user evaluation, we have studied how the performance of the MOS tools are affected by the geometric configuration of the objects to be selected. Our studies demonstrate that the performance of MOS techniques is very significantly affected by the geometric scenario facing the user. Furthermore, we demonstrate that a good match between MOS tool shape and the geometric configuration is not always preferable, if the applied tool is complex to use.

Enabling users to shape 3-D boxes in immersive virtual environments is a non-trivial problem. In this paper, a new family of techniques for creating rectangular boxes of arbitrary position, orientation, and size is presented and evaluated. These new techniques are based solely on position data, making them different from typical, existing box shaping techniques. The basis of the proposed techniques is a new algorithm for constructing a full box from just three of its corners. The evaluation of the new techniques compares their precision and completion times in a 9 degree-of-freedom (DoF) docking experiment against an existing technique, which requires the user to perform the rotation and scaling of the box explicitly. The precision of the users' box construction is evaluated by a novel error metric measuring the difference between two boxes. The results of the experiment strongly indicate that for precision docking of 9 DoF boxes, some of the proposed techniques are significantly better than ones with explicit rotation and scaling. Another interesting result is that the number of DoF simultaneously controlled by the user significantly influences the precision of the docking.