Presence

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See also: Social presence

Presence is the feeling of being physically and spatially located in an environment. VR allows us, for the first time, to feel Presence in another realm, in a virtual realm. It is one of the most important yet indescribable factors of VR.

Presence can be divided into 2 types: Cognitive Presence and Perceptive Presence. Cognitive Presence is the presence of your mind. It can be achieved by watching a compelling film or reading an engaging book. Cognitive Presence is important to an immersive experience of any kind. Perceptive Presence is the presence of your senses. To accomplish Perceptive Presence, your senses, sights, sound, touch and smell, have to be tricked. Perceptive Presence can only be achieved by Virtual Reality and Augmented Reality.

Immersion is different from Presence. The former means that you feel surrounded by or the virtual world while the latter means that you feel you are within the virtual world. Presence is achieved when the involuntary aspects of our reptilian corners of our brains are activated. When the user reaches out to grab the virtual apple, becomes unwilling to step off a plank or feel nervous when walking on rooftops.

Virtual Reality

Presence is the most crucible aspect to a true virtual reality experience. To have an effective VR, The user has to feel that he or she is within the artificially created world. This is the only way to elicit emotions and involuntary, reflex-like reactions from the user.

To create Presence, the VR Device has to fool the user's senses, most notably the audio-visual system. VR Devices achieves this through head tracking HMDs. The movement of the user's head changes his or her viewpoint based on the movement. The goal of the device is maintain your sense of presence and avoid breaking it. The behavior of objects in the virtual environment has to meet the expectations of the user.

While VR relies on Presence, VR is also one of few media that can create Presence.

Requirements for Presence

Tracking

  • 6 degrees of freedom tracking - ability to track user's head in rotational and translational movements.
  • 360 degrees tracking - track user's head independent of the direction the user is facing.
  • Sub-millimeter accuracy - tracking accuracy of less than a millimeter.
  • No jitter - no shaking, image on the display has to stay perfectly still.
  • Comfortable tracking volume - large enough space to move around and still be tracked.[1]

Latency

  • Less than 20 ms motion-to-photon latency - less than 20 milliseconds of overall latency (from the time you move your head to when you see the display change).
  • Fuse optical tracking and IMU data -
  • Minimize loop: tracker → CPU → GPU → display → photons.[1]

Persistence

  • Low persistence - Turn pixels on and off every 2 - 3 ms to avoid smearing / motion blur.

Resolution

  • Correct stereoscopic 3D rendering
  • At least 1k by 1k pixels per eye
  • No visible pixel structure - you cannot see the pixels.[1]

Optics

  • Comfortable eyebox - the minimum and maximum eye-lens distance wherein a comfortable image can be viewed through the lenses.
  • High quality calibration and correction - correction for distortion and chromatic aberration that exactly matches the lens characteristics.[1]

Augmented Reality

Presence is equally important to an immersive AR experience. To achieve Presence in Augmented Reality, seamless integration of virtual content and physical environment is required. Like in VR, the virtual content has to align with user's expectations. One theory is that to have truly immersive AR, user cannot discern virtual objects from real objects.

Additional reading

http://www.ehrssonlab.se/publications.php

http://webstaff.itn.liu.se/~matco/TNM053/Papers/presence.pdf

References

  1. 1.0 1.1 1.2 1.3 1.4 Oculus Connect 2014: Brendan Iribe Keynote