Vision

“Your vision will become clear only when you look into your heart. Who looks outside, dreams. Who looks inside, awakens.” – Carl Jung

Perhaps we will show Jung wrong when we develop technology that lets us look into ourselves by looking outward – W.O.M.B.

What qualities do our vision senses require for immersion?

There are 8 depth cues that deliver spatial information in what we see:

1. Occlusion (hidden surfaces)
2. Perspective Projection (parallel lines meet at infinity)
3. Binocular Disparity (each eye sees a different view)
4. Motion Parallax (due to head motion)
5. Convergence (rotation of the eyes to view a close object)
6. Accommodation (change of shape of eye to view a close object - focus)
7. Atmospheric (fog)
8. Lighting and Shadows

All of the above can be accomplished with current technology with the exception of accommodation - VRD

Stereoscopic Vision

The majority of our spatial clues do not require binocular disparity, in fact we only use it to gauge distance when objects are within a few feet of us.

There are 2 major techniques for delivering different images to each eye:

Projection Based Techniques

• The image source contains the content intended for each eye
• Red/Green filters used since the 50's in 3D films
• Modern 3D films use diffraction grating
• Shutter glasses allow the use of a simple time sequencing – Crystal Eyes

Head Mounted Techniques

• The image source is located in front of each eye
• Early stereo viewers from the early 1900’s
• Ivan Sutherland’s first experiments used a head mounted display
• Due to their heaviness, some HMD’s use a counterweighted boom

Both techniques have advantages and disadvantages:

Projection Based Techniques

• usually can deliver greater resolution
• usually deliver viewer comfort because the device is not on the user’s head
• range of motion is restricted to the location encompassed by the display
• less likely to cause disorientation because the user is also aware of their physical surroundings

Head Mounted Techniques

• usually allow a much more natural interaction with the display because they move with the user
• require more accurate tracking because motion delays are more unsettling
• range of motion is only limited to the length of cords or wireless transmission
• can gain the advantages of physical awareness by using a semi-occluding screen (i.e. augmented reality)

What is the relationship to input?

The output of stereoscopic immersive display systems will only be as good as the tracking ability of the system.

Tracking Techniques

Mechanical

• highly accurate
• low latency
• highly encumbering
• only allow single object to be tacked in the same space (1 sensor)

Sonic

• highly accurate
• high latency (sound travels slowly)
• low encumberence
• allows multiple sensors

Optic

• high/low accuracy
• high latency (due to processing)
• unencumbering when using a low number of markers/long setup time when seeking high accuracy
• allows multiple sensors
• suffers from occlusion problems that may lead to inaccurate results under common situations

Magnetic

• medium accurate
• medium latency (speed of light on wires)
• medium encumbering (lightweight wires can be used)
• allows multiple sensors
• inexpensive

The InterSence IS-900 uses sound for accurate position and accelerometers for fast response