depth perception and visualization matt williams from:
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Depth Perception and Visualization
Matt Williams
From: http://www.cs.washington.edu/homes/cassidy/tele/index.html
Depth Perception and Visualization References and borrowed images: Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San
Fancisco: Morgan Kaufmann. J.D. Pfautz, Depth Perception in Computer Graphics, Doctoral Dissertation,
University of Cambridge, UK, 2000. C. Ware, C. Gobrecht, and M.A. Paton, "Dynamic Adjustment of Stereo Display Parameters,"
IEEE Transactions on Systems, Man and Cybernetics---Part A: Systems and Humans, Vol. 28, No. 1, Jan. 1998, pp. 56-65.
www.wlu.ca/~wwwpsych/tsang/8Depth.ppt(no author provided) Robertson,G.,Mackinlay,J.,&Card,S.ConeTrees: Animated 3D visualizations of hierarchical
information. In Proceedings of CHI'91 (New Orleans, LA), ACM, 189-194. WANGER, L., FERWANDA, J., AND GREENBERG, D. 1992. Perceiving spatial relationships in
computer generated images. IEEE Computer Graphics and Applications (May) 44-58.
Depth Perception and Visualization
Depth Perception Cues How do we combine these cues to perceive
depth InfoVis Application
Which cues are helpful? Which cues may be important in your
project?
Depth Cues Monocular
Perspective Cues Size Occlusion Depth of Focus Cast Shadows Shape from Motion
Binocular Eye Convergence Stereoscopic depth
Structure from Motion Motion Parallax Kinetic Depth
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Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Structure from Motion Kinetic Depth Effect Assumption of rigidity allows us to
assume shape as objects move/rotate
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Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Perspective Cues Parallel lines converge Distant objects appear smaller Textured Elements become smaller
with distance
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Perspective Cues
http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Perspective Cues Taking advantage of linear perspective
in visualization
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Perspective Cues Size Constancy Perception of actual size versus retinal size. Can perceive 2D picture plane size for sketchy
images (see below)
http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Perspective Cues
http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Perspective Cues
http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Perspective Cues Usually we percieve images on the
computer from the wrong viewpoint Robustness of linear perspective (Kubovy, 1986)
e.g Movie Theatre
Why might we want to correct for viewpoint changes (head movement) anyway?
Motion Parallax Placement of virtual hand or object
Perspective Cues Placement of virtual hand or object Need for head coupled perspective
vrlab.postech.ac.kr/vr/gallery/edu/vr/display.ppt
Occlusion The strongest depth cue.
http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Depth of Focus Strong Depth Cue Must be coupled with user input (e.g.
point of fixation) Computationally expensive
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Cast Shadows Important cue for height of an object above a
plane An indirect depth cue Shown to be stronger than size perspective
(Kersten, 1996)
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Shape From Shading
Ware Chapter 7http://www.wlu.ca/~wwwpsych/tsang/8Depth.ppt
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Eye Convergence
Better for relative depth than for absolute depth
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Stereoscopic Depth How it works Two different views fuse to one
perceived view (try it)
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Right eyeScreen
Left eye
Panum's Fusional Area
disparity = -
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Stereoscopic Depth Panum’s fusional area Range before diplopia occurs(worst case):
Fovea – 1/10 of a degree (3 pixels) Periphery – 1/3 of a degree (10 pixels)
Factors for Fusion Moving images Blurred images Size Exposure
Stereoscopic Depth
velab.cau.ac.kr/lecture/Stereo.ppt
Stereoscopic Depth Problems with stereoscopic displays Diplopia occurs when images don’t fuse (try it)
Diplopia reduced for blurred images – great for the real world but …
Stereoscopic displays only contain sharp images. Close-up unattended items can be obtrusive.
Vergence Focus Problem Everything on the computer screen is on the same focal
plane. Causes eyestrain
Frame Cancellation:
Stereoscopic Depth Frame Cancellation:
Solution?
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Stereoscopic Displays Cyclopean Scale
Move virtual environment close to the display plane
No Cancellation Reduced Vergence-focus problem
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Stereoscopic Displays Virtual Eye Separation
(Telestereoscope) Allows for a decrease or
increase in disparity Allows for an increase or
decrease in the depth of the virtual environment
http://www.cs.washington.edu/homes/cassidy/tele/index.html
Depth Perception Theory General Unified Theory
Perceived Depth = Weighted sum of all Depth Cues Rank the cues in importance e.g.
Occlusion Motion Parallax Stereo Size constancy Etc.
Depth Perception Theory Importance changes with distance
, 96, 96
Cutting, 1996
Depth
Con
trast
Depth (meters)
Occlusion
1 10 100
Size constancy
Cast Shadows
Stereo
Motionparallax
Convergence
Aerial
Space Perception Theory Task Dependant Model
Cues weights are combined differently based on the task Evidence?
Task: Orientation of a virtual Object• Cast Shadows and Motion Parallax help
• But …Linear Perspective hinders such orientation Task: Object translation
• Linear perspective was the most useful cue
Wanger, 1992
InfoVis Tasks: Tracing 3D data paths Judging 3D surfaces Finding 3D patterns of points Relative Position in 3D space Judging movement of Self Judging Up Direction Feeling a “sense of Presence”
Tracing 3D Data Paths Benefits of 3D Trees
More nodes can be displayed (Robertson et al., 1993)
Reduced errors in detecting Paths (Sollenberger and Milgram, 1993)
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Tracing 3D Data Paths
Beneficial Cues: Kinetic Depth and Stereoscopic
Depth reduced errors in path detection
Kinetic Depth was the stronger cue Occlusion Is helpful (Ware and Franck, 1996)
3D Patterns of Points
http://www-pat.fnal.gov/nirvana/plot_wid.htmlhttp://neutrino.kek.jp/~kohama/sarupaw/sarupaw_html/fig/nt_3d.gif
3D Patterns of Points
Beneficial Cues: Structure from motion Stereo Depth
Not Beneficial: Perspective Size Cast Shadows Shape from Shading (How?)
3D Patterns of Points
Add shape to clouds of points
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Judging Relative Position
Small Scale (Threading a needle) Beneficial: Stereo Not Beneficial: Motion Parallax
Large Scale ( > 30 m) Beneficial: motion parallax,
perspective, cast shadows, texture gradients
Not Beneficial: stereo
Ware, C., Chapter 8 of Information Visualization: Perception for Design. 2000, San Fancisco: Morgan Kaufmann.
Conclusion Depth Cues Existing Theories Application to InfoVis
Occlusion Texture
Gradient Size Constancy Cast Shadows Stereo
From: http://www.cs.washington.edu/homes/cassidy/tele/index.html