Passive haptics significantly enhances virtual environments

University of North Carolina at Chapel Hill Ph.D Dissertation (2001),
Experiments
Tasks
Findings

They evaluated participants' sense of presence with or without passive haptics in a VE.

Variables and Constants

    Haptic Fidelity
  • haptic quality - passive haptics of the floor or no haptics at all.
Constants

The same virtual environment was used in both the passive haptic and no haptic condition.

System Info

Displays
  • head-mounted display - a virtual research v8 head-mounted display with true vga resolution of (640x3) x 480 pixels per eye was used in both experiments. this display device consists of two 1.3-inch-diagonal active matrix lcds with an aspect ratio of 4:
Input Hardware
  • hiball head tracker sensor - this tracker works over a range of 10m by 4m with 0.2 millimeter positional resolution and angular precision better than 0.03 degree. it updates position and orientation at approximately 1.5khz. these updates are filtered over 25 ms before they are sent
  • polhemus 3space 6dof tracker - for tracking of links on the participants' knees and another in a joystick held by one hand
  • joystick - handheld, tracked by the polhemus

One graphics pipe of a Reality Monster, a 32-processor SGI Onyx2 computer, was used to generate the images. The pipe consists of an Infinite Reality2 Engine with four R12000 processors, four raster managers, and 64MB texture memory. The system maintained a frame update rate of 20 to 30 Hz stereo.

Participant Info

36/52 male Recruited from undergrad computer science courses The following criteria were used to exclude participants before the start of the experiment: • Participants who could not use stereopsis for depth perception, • Participants who were not ambulatory, • Participants with a history of epilepsy, seizures, or strong susceptibility to motion sickness, • Participants who reported not being in their usual state of good physical fitness at the time of the experiment (including participants who recently used sedatives, tranquilizers, decongestants, anti-histamines, alcohol, or other medication), • Participants uncomfortable with the system, or who had difficulty fitting the display to their heads (a brief demonstration was done at the beginning of the session), • Participants who had more than three prior exposures to a virtual reality system.

Total # Age Range Gender Balance
52 18 - 45

While wearing the head-mounted display in the Training Room, participants were trained to pick up and move objects. After training, participants were instructed to carry a virtual book into the virtual Pit Room through a previously closed door, carry it to the other side of the room, and place it on the chair.

Interaction and Environment

Interface

The virtual book was directly mapped to the hands.

The virtual environment consisted of the Training Room and the Pit Room. The Pit Room consisted of a 2-foot wide virtual ledge above a 20-foot (virtual) drop to a room below containing living room furniture. There was also a chair on the wooden ledge on the far side of the room.

Dimensionality Scale Density Visual Realism
3D Large Medium Medium
Metrics

  • presence - presence was measured in three components: subjective presence, observed behavioral presence (through behaviors found with video analysis), and physiological presence.
  • cybersickness - they used a used a simulator sickness questionnaire.
  • heart rate - finger skin temperature, electrodermal response (galvanic skin response), and heart rate (via a three electrode electrocardiography) were measured non-invasively from the fingers of one hand using procomp+ tethered telemetry system at a rate of 32 times p
  • user task perception - subjective presence was measured by the ucl presence questionnaire
  • strategy - observed behavioral presence was measured by scoring key movements, thought to be reactions to the virtual pit, post-session from videotapes.
  1. There was a significant direct effect of haptic quality on presence for a interactive experience of the ve task.

    Adding passive haptics led to higher sense of presence in navigating in a VR with a pit room.

    Specificity: Somewhat general
    Those who experienced passive haptics exhibited significantly more behaviors associated with pit avoidance than participants who did not experience passive haptics, (p < 0.001).

  2. There was a significant direct effect of haptic quality on heart rate for a interactive experience of the ve task.

    Adding passive haptics led to both higher heart rate and skin conductivity than without haptics for walking through a VE with a pit room.

    Specificity: Neither
    Physiological measures showed significantly higher changes in heart rate (p < 0.05) and skin conductivity (p < 0.05)

This study had two goals. First, to show whether participants form better cognitive maps of the virtual environment when the VE is augmented with passive haptics. The second goal was to show whether participants perform a real-world navigation task better after training in a VE augmented with passive haptics than after training in a purely visual VE.

Variables and Constants

Constants

Display-related info such as display form factor, pixel resolution, among others, are constant.

System Info

Displays
  • head-mounted display - a virtual research v8 head-mounted display with true vga resolution of (640x3) x 480 pixels per eye was used in both experiments. this display device consists of two 1.3-inch-diagonal active matrix lcds with an aspect ratio of 4:
Input Hardware
  • hiball head tracker sensor - this tracker works over a range of 10m by 4m with 0.2 millimeter positional resolution and angular precision better than 0.03 degree. it updates position and orientation at approximately 1.5khz. these updates are filtered over 25 ms before they are sent
  • polhemus 3space 6dof tracker - for tracking of links on the participants' knees and another in a joystick held by one hand
  • joystick - handheld, tracked by the polhemus

One graphics pipe of a Reality Monster, a 32-processor SGI Onyx2 computer, was used to generate the images. The pipe consists of an Infinite Reality2 Engine with four R12000 processors, four raster managers, and 64MB texture memory. The system maintained a frame update rate of 20 to 30 Hz stereo.

Participant Info

All were college students. The following criteria were used to exclude participants before the start of the experiment: • Participants who could not use stereopsis for depth perception, • Participants who were colorblind, • Participants who were not ambulatory, • Participants with a history of epilepsy, seizures, or strong susceptibility to motion sickness, • Participants who reported not being in their usual state of good physical fitness at the time of the experiment (including participants who had recently used sedatives, tranquilizers, decongestants, anti-histamines, alcohol, or other medication), • Participants uncomfortable with the system, or who had difficulty fitting the display to their heads (a brief demonstration was done at the beginning of the session). No participants were excluded from the study based on these criteria.

Total # Age Range Gender Balance
33 19 - 23

The task was to gain as much information about the layout of the environment as possible. Participants knew before the VE session that their training would be tested by navigating an identical real environment blindfolded. Participants walked three laps around the environment and were instructed to touch the various objects in the room.

Interaction and Environment

Interface

The camera was directly mapped to their position in the maze. No other interactions were used.

The virtual environment used in this experiment was constructed from rectangular solids of various sizes. Objects were colored gray, red, green, blue, and yellow. To prevent participants from getting information about object size from textures, no textures were used on the objects. Patterned textures were used on the walls, floor and ceiling to prevent disorientation.

Dimensionality Scale Density Visual Realism
3D Medium Low Low
Metrics

  • training transfer - sketch maps were used to assess the participants ability to encode, store and decode cognitive mapping information
  • errors - number of wrong turns and bumps hit in the real-world maze
  • time - time to complete maze
  1. There was a significant inverse effect of haptic quality on time for a comprehension of spatial information task.

    Adding passive haptics along with a VE of a maze led to faster completion times for navigating through a real-world maze.

    Specificity: Neither
    A MANOVA revealed a statistically significant difference (p < 0.05) in the time to complete the blindfolded navigation between the group trained in an augmented VE (Mean = 64.6 seconds) and the group trained in a non-augmented VE (Mean = 100.8 seconds).

  2. There was a significant inverse effect of haptic quality on errors for a comprehension of spatial information task.

    Adding passive haptics in a VR tour of a maze led to fewer collisions in navigating the real-world equivalent of the same maze.

    Specificity: Somewhat specific
    The group that trained with passive haptics navigated with fewer collisions with objects, (p < 0.05).