Mats Lind

2D vs 3D, implications on spatial memory

Since the introduction of graphical user interfaces (GUI) and two-dimensional (2D) displays, the concept of space has entered the information technology (IT) domain. Interactions with computers were re-encoded in terms of fidelity to the interactions with real environment and consequently in terms of fitness to cognitive and spatial abilities. A further step in this direction was the creation of three-dimensional (3D) displays which have amplified the fidelity of digital representations. However, there are no systematic results evaluating the extent to which 3D displays better support cognitive spatial abilities. The aim of this research is to empirically investigate spatial memory performance across different instances of 2D and 3D displays. Two experiments were performed. The displays used in the experimental situation represented hierarchical information structures. The results of the test show that the 3D display does improve performances in the designed spatial memory task.

The art of the obvious

In addition to normal reading, knowledge can be gained from a paper document by pattern recognition and encoding of characteristics of the information media. There are reasons to believe that this can be done automatically with very little attentional demand. The knowledge gained is accessible to consciousness and can be used for task components like orientation, navigation, detection of changes and as a complement to normal reading. When information is computerized, and is read from a screen instead of from a paper, the conditions for automaticity are often radically changed. In most cases the reader has to gain the corresponding knowledge by effortful cognitive processes. This means adding to the cognitive load leaving less attentional capacity for the main task at hand. This problem can be avoided by a careful analysis of a reading task into its automatic and non-automatic components, followed by a dedicated user interface design where information relevant for orientation, navigation, etc. is presented in a way that the reader can perceive rather than read.

Evaluating 2D and 3D visualizations of spatiotemporal information

Time-varying geospatial data presents some specific challenges for visualization. Here, we report the results of three experiments aiming at evaluating the relative efficiency of three existing visualization techniques for a class of such data. The class chosen was that of object movement, especially the movements of vehicles in a fictitious landscape. Two different tasks were also chosen. One was to predict where three vehicles will meet in the future given a visualization of their past movement history. The second task was to estimate the order in which four vehicles arrived at a specific place. Our results reveal that previous findings had generalized human perception in these situations and that large differences in user efficiency exist for a given task between different types of visualizations depicting the same data. Furthermore, our results are in line with earlier general findings on the nature of human perception of both object shape and scene changes. Finally, the need for new taxonomies of data and tasks based on results from perception research is discussed.

Metric 3D structure in visualizations

A large body of results on the characteristics of human spatial vision suggests that space perception is distorted. Recent studies indicate that the geometry of visual space is best understood as affine. If this is the case, it has far-reaching implications on how 3D visualizations can be successfully employed. For instance, all attempts to build visualization systems where users are expected to discover relations based on Euclidean distances or shapes will be ineffective. Since visualization can, and sometimes does, employ all possible types of depth information and because the results from vision research usually concentrates on one or two such types, three experiments were performed under near-optimal viewing conditions. The aim of the experiments was two-fold: to test whether the earlier findings generalize to shape perception under near-optimal viewing conditions and to get a sense of the size of the error under such conditions. The results show that the findings do generalize and that the errors are large. The implications of these results for successful visualizations are discussed.

Large continuous perspective transformations are necessary and sufficient for accurate perception of metric shape

We investigated the ability to perceive the metric shape of elliptical cylinders. A large number of previous studies have shown that small perspective variations (#10°) afforded by stereovision and by head movements fail to allow accurate perception of metric shape. If space perception is affine (Koenderink & van Doorn, 1991), observers are unable to compare or relate lengths in depth to frontoparallel lengths (i.e., widths). Frontoparallel lengths can be perceived correctly, whereas lengths in depth generally are not. We measured reaches to evaluate shape perception and investigated whether larger perspective variations would allow accurate perception of shape. In Experiment 1, we replicated previous results showing poor perception with small perspective variations. In Experiment 2, we found that a 90° continuous change in perspective, which swapped depth and width, allowed accurate perception of the depth/width aspect ratio. In Experiment 3, we found that discrete views differing by 90° were insufficient to allow accurate perception of metric shape and that perception of a continuous perspective change was required. In Experiment 4, we investigated continuous perspective changes of 30°, 45°, 60°, and 90° and discovered that a 45° change or greater allowed accurate perception of the aspect ratio and that less than this did not. In conclusion, we found that perception of metric shape is possible with continuous perspective transformations somewhat larger than those investigated in the substantial number of previous studies.

The interface is often not the problem

Computer systems in the form of tools for specific functions within a work environment are becoming increasingly common. Because the users are not computer experts, and because the introduction of the new tools can dramatically change their tasks, problems arise. It is argued that even if the proper design of the MMI is very important, this will not solve all the problems. More basic problems concern what functions should be included in the system and how the users can understand what the system can do in different work situations and how the response should be evaluated in the context of the work situations. This is demonstrated by experiences from application projects. It is concluded that more research must be devoted to these problem areas. Another important result is the fact that the possibilities to develop more generally applicable computer based tools are limited. Adaption to local circumstances and needs is usually a necessity.

Analysis of information utilization (AIU)

Analysis of information utilisation (AIU) is a method for specifying how information entities encountered in information analysis are being physically manipulated in the work situation undergoing a ...

The effect of polar projection on the perception of euclidean structure from motion.

The aim of the present study was to examine whether euclidean structure could be recovered from apparent motion sequences under polar projection. In Experiment 1, length judgments of two sides of a simulated triangle rotating in depth did not reveal effects of type of projection, polar or parallel, on the perception of euclidean structure. However, there was a significant correlation between simulated and produced slants. The results also indicated that absolute depth judgments could not be accounted for by a random mechanism suggested by Todd and Bressan (1990). Experiments 2 and 3, in which a continuous dot surface was substituted for the triangle, showed that polar projection information from a relatively large visual angle, 17.40°, as compared with a small visual angle, 4.35°, facilitated discrimination of depth. Produced height:width ratios were consistently related to simulated shape, although the depth dimension was underestimated. Finally, Experiment 4 showed significant correlations between simulated and produced height:width ratios that could be accounted for only by an analysis in whichX andY velocities were treated independently. As in previous experiments, the variation in the depth dimension was underestimated. It was concluded that the visual system utilizes the additional information that is available in polar projection when recovering structure from motion, but that for different reasons the perceived structure does not become euclidean. These reasons are discussed briefly.

Surface glyphs for efficient visualization of spatial multivariate data

We present a first effort to evaluate the possible utility of a new type of surface glyphs intended for visualizations of multivariate spatial data. The glyphs are based on results from vision research suggesting that our perception of metric 3D structure is distorted and imprecise relative to the actual scene before us; only a class of qualitative properties of the scene is perceived with accuracy. These properties are best characterized as being invariant over affine but not Euclidean transformations. A large number of possible 3D glyphs for the visualization of spatial data can be constructed using such properties. One group of such glyphs is based on the local sign of surface curvature. We investigated this group in two visualization experiments. The results show that available sources of 3D structural information were sufficient for our subjects to make fast and accurate judgments. Some implications for visualization are also discussed.

Perceiving motion and rigid structure from optic flow: A combined weak-perspective and polar-perspective approach

Structure-from-motion algorithms based on weak-perspective projection have many interesting properties and could serve as a basis for a model of human perception of motion and structure from motion (M&SFM). There is some psychophysical evidence, however, that points to discrepancies between what can be accomplished with these algorithms and the performance of human subjects in certain M&SFM tasks. In light of this evidence, this paper presents a mechanism that both takes advantage of all the possibilities offered by a weak-perspective approach and behaves in a manner that is in close correspondence with human performance in M&SFM tasks. It consists of a novel weak-perspective—based method operating at small visual angles and a complementary, perspective-projection—based method operating at larger visual angles.