COMS W4172 Travel 3 - cs.columbia.edu

Feiner, COMS W4172, Spring 2021

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COMS W4172Travel 3

Steven FeinerDepartment of Computer ScienceColumbia University New York, NY 10027

www.cs.columbia.edu/graphics/courses/csw4172

March 18, 2021

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Target SelectionSelect Target to Stand on in World User selects target on horizontal surface through ray

pointing (e.g., from controller) Problem: Straight ray can be blocked by intermediate

objects or destination is above ray origin Solution: Use curved ray (e.g., parabola)

https://aframe.io/blog/teleport-component/


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Target Selection (with a passenger)Select Target to Stand on in World Navigator specifies target with ray,

passenger accompanies at offset Problem: It is unclear where passenger will land Solution: Show ray for passenger from their controller

https://www.uni-weimar.de/en/media/chairs/computer-science-department/vr/research/multi-user-virtual-reality/multi-ray-jumping/

T. Weissker et al., Multi-Ray Jumping, IEEE VR 2019

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Target SelectionHead Butt “Zoom” Mine, Brooks, & Sequin, 1997

User image-plane selects object of interest System leaves frame (“portal”) in air User “butts” head into frame

to move forward, pullshead out to return to original position User can quickly switch

between two viewpointshands-free User can step forward to move to new

view for an extended time,back to return

Mine, Brooks, & Sequin, 1997

Dolly, not zoom!


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Manual Manipulation of Viewpoint

User manipulates viewpoint as if manipulating an object

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Manual Manipulation of ViewpointFixed-Object Manipulation

User selects object, acts as if manipulating it, but viewpoint is changed instead (e.g., differentiate based on button pressed) Image-plane select object,

move hand(s) closer to eye to move to object (Pierce et al. 1997) Scaled-world grab object,

move self relative to object (Mine, Brooks, Sequin 1997)


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Manual Manipulation of ViewpointGrabbing the Air If user selection action

(grabbing) doesn’t select a movable object, then select the entire world

Translate world origin (but ignore rotation to avoid confusion)

Use two hands as if pulling a rope (Mapes & Moshell, 1995)

Can be tiring

, where and are old

and new world positions, and and

are old and new dominant hand positions

d d

d d

w' w n' n w w'

n n'Variation: Image-plane select with hands outside of designated area (yellow outline) during trigger grabs air for travel. (Based on observation that users positioned hands away from center of image plane when grabbing air.J. Pierce, 2001

J. Pierce, 2001

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Travel by Scaling

Scale down world (Scale up user) Move Scale up world (Scale down user) E.g., S. Bryson & C. Levit, IEEE

Visualization 91; J. Butterworth et al., 92

Note difference between scaling position of head vs. scaling head (and IPD!)

Use virtual body to help user understand scale

Scaling Affects precision May cause VR sickness in egocentric

environment if smooth/continuous


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Controlling Viewing Orientation

Head tracking Natural Improves spatial understanding

Orbital viewing (J. Chung, I3D 92) Select position p and distance r Head rotations are mapped to move viewpoint on

surface of sphere with center p and radius r, looking at p Look left, right, up, down to see object’s right, left, bottom,

top, respectively

Good for inspection of one object at p, but… Can be confusing with more objects in environment Can cause VR sickness

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Nonisomorphic rotation Modify treatment of user

orientation while walking Redirected Walking (S.

Razzaque) Provide user with experience of

walking in a much larger environment

m°real rotation ~ ½ m°virtual rotation https://youtu.be/o92bG1_YGDM

Inject most of distortion while changing physical orientation, add the rest while walking

S. Razzaque, Z. Kohn, and M. Whitton, Eurographics 2001

Path invirtual room

Path inreal room

2:33–3:18


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Redirected walking with distractors Distract user attention while

distorting the mapping of real orientation to virtual orientation E.g., virtual butterfly flutters in

front of the user while walking in a virtual outdoor environment

T. Peck, M. Whitton, and H. Fuchs, IEEE VR 2008

Path invirtual room

Path inreal room

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Change Blindness

RA Rensink, https://www2.psych.ubc.ca/~rensink/flicker/


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Redirection by Change BlindnessE. Suma et al., VR 2011

Change Blindness Failure to notice a large visual change

when attention is distracted from the change

For general information/examples, seehttps://www.youtube.com/watch?v=bh_9XFzbWV8http://www2.psych.ubc.ca/~rensink/flicker/

Change location of virtual door while user isn’t looking

With right environment design, trick user into thinking they’re navigating a larger environment with a different layout

Before

After

Above: What user would see if they looked behind after entering roomBelow: What user sees after performing task before leaving room

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Virtual environment (60‘ x 60‘) Real environment (14‘ x 14‘)

Door is moved and room size changes when user nears desk

User enters room A below User exits and prepares to enter room B below in same location

A B

User believes that room B is on the same corridor as room A

User’s path to room A and then on to room B in the same virtual corridor includes right turn at corner of real environment


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Questionnaire Mean

outcome questions (blue) embedded in decoy questions

Only one participant of 77 in two studies definitively noticed a scenechange

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Impossible Spaces E. Suma et al., IEEE TVCG 2012

Create virtual environment in which rooms overlap User sees only one of a set of overlapping rooms at a time User travels between spaces by following a path intended to hide the deception Can also generate the rooms on the fly for larger environments (e.g., Sra et al.,

VRST 2016, Cheng et al., VR 2019)

Possible Impossible


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Redirection for Hand-HeldsO. Oda & S. Feiner, ISMAR 2009

AR Domino Knockdown Two-player FPS

Knock down other player’s dominos by shooting balls from screen

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How to avoid unwanted physical collisions? Redirected Motion Shifts virtual location

of tracked device ahead of physicallocation as one player moves toward another player Shifts back as first

player retreats

Inspired by Redirected Walking [S. Razzaque et al. 2001]


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Redirected Motion: Green Player’s POV

With ShiftWithout Shift

Ghost views of displays show virtually shifted locations

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Redirected Motion: Third-Person POV


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User study Compared 9 pairs of

participants playing with/without redirected motion, and other techniques Redirected motion Kept users farther

apart Was undetectable

when used with parameters set in pilot study

COMS W4172 Travel 3 - cs.columbia.edu

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