Studying the Effects of Stereo, Head Tracking, and Field of Regard on a Small-Scale Spatial Judgment Task

IEEE Transactions on Visualization and Computer Graphics (2013), pp. 886-896, doi: 10.1109/TVCG.2012.163
Experiments
Tasks
Findings

The goal of the experiment was to study the effects of stereoscopy, head tracking, and field of regard on performance of a spatial understanding task requiring spatial judgments of small-scale structural features.

Variables and Constants

Independent Variables
  • head tracking - whether or not positional head tracking was enabled. levels: on; off
Constants

Display size, field of view, form factor, frame rate, latency, refresh rate, pixel density, software FOV. No audio or haptics in any condition. Interaction technique for virtual navigation of the dataset. Scenario fidelity.

System Info

Displays
  • surround screen display - participants viewed the 3d structures within a four-screen cave projection display using 1;280 ???? 1;024 electrohome crt projectors. the cave display consisted of three rear- projected walls measuring 100 wide and 90 high and a front- projected floor mea
Input Hardware
  • is900 - intersense is-900 wired head tracker
  • is900 - intersense is-900 wireless wand with joystick
Software

Participant Info

68 percent of participants were younger than 30 years of age. The mean age was 27.5 and the median was 21.5 years.

Total # Age Range Gender Balance
52 18 - 68

For the experimental task, participants inspected virtual 3D models of complex, underground cave structures. Eleven similar models were created based on a real cave-maze layout (a structural layout of multiple intersecting path- ways). For each model, the structure was designed with four horizontal layers of interconnecting cave tubes (see Fig. 2). These horizontal layers of networking tubes were connected by several vertical tube paths. For each experimental trial, participants inspected the cave structures and counted the number of vertical tubes that connected the horizontal layers. The models also included vertical tubes that did not connect between levels. The presence of these tubes complicated the task; careful inspection was required in order to determine whether or not a vertical tube actually connected horizontal levels.

Interaction and Environment

Interface

Participants used an InterSense tracked six degree-of- freedom wand with a joystick for navigation. Participants could point the wand in the direction they wished to travel and push the joystick forward or backward in order to move in the desired direction. Additionally, participants could rotate the virtual world along the vertical axis by moving the joystick to the left or the right. Navigation was not restricted by collisions with the tube structures; participants were free to navigate through the 3D model. Regardless of condition or positioning in the virtual space, the system’s frame rate remained at approximately 60 fps. Additionally, users could physically rotate to see different parts of the model, and could physically translate in the head tracking conditions to change their view.

The structure models were smooth-shaded and colored according to elevation, making each horizontal tube layer a consistent color. The vertical tubes between horizontal layers were colored with a gradient between the colors of its two enclosing horizontal layers. Participants viewed the structure against a white background. Model dimensions were designed with approximately a 3:1:3 ratio for x:y:z (with y being the vertical dimension). The models were scaled to roughly fit entirely inside the CAVE’s 100 by 100 horizontal display space. The tube-structure models were designed to exhibit approximately equal levels of structural complexity. All structures included 15 vertical tubes. In each model, some of these 15 tubes (between 3 and 12) made connections between the horizontal levels, while others did not (see Fig. 3). One of the models was used for the training session and the other 10 were used for the experiment trials. All participants viewed the models in the same order.

Dimensionality Scale Density Visual Realism
3D Small Low Low
Metrics

  • time - logged automatically by the system
  • errors - participants' answers compared to ground truth
  1. There was a significant inverse effect of head tracking on errors for a comprehension of spatial information task

    There was a significant main effect of head tracking on task errors, with F(1, 44) = 4.54 and p < 0.05. The number of errors with head tracking (M = 0.66, SD = 0.38) was significantly less than the number of errors without head tracking (M = 0.87, SD = 0.

    Specificity: Somewhat general
    The task was a detailed spatial judgment task.

  2. There was a significant inverse effect of field of regard (for) on errors for a visual search task.

    A significant main effect of FOR on errors, with F(1, 44) = 8.95 and p < 0.01. Significantly fewer errors were made in the high FOR conditions (M = 0.61, SD = 0.37) than in the low FOR conditions (M = 0.92, SD = 0.37).

    Specificity: Somewhat general

  3. There was a significant interaction between stereoscopy and head tracking on time for a visual search task.

    The analysis also revealed a significant interaction between head tracking and stereo, with F(1, 44) = 5.43 and p < 0.05, which explained the significant effects of these components individually. A post-hoc Tukey HSD analysis showed that the combination o

    Specificity: Somewhat general