Space Perception

Depth Cues Tasks Shape-from-Shading

Perception of surface shape

Simple lighting model Light from above and at infinity Specular, Diffuse and Ambient

components Oriented texture can enhance shape

perception

Lighting model

Lambertian, specular, ambient + cast shadows

Standard lighting model

Specular refection

diffuse reflection =lambertian

Ambient illumination

Examples

ShadingSpecular reveals fine detail

Cushion Tree Map Jarke Van Wijk

Contour and Shading

Textures for surface orientation (Interrante)

Lighting

Simple lighting model Not photorealistic Single light source from above and at

infinity Specular for detail Cast shadows if scene is simple

The 3D vs 2D debate

Should we display abstract data in 3D? Depth cue theory Depth cues are environmental information

that tell us about space Can be applied somewhat independently

Occlusion: The strongest depth cue

Perspective

Perspective

Perspective (Cockburn and McKenzie)

PerspectivePicture plane positionOcclusion

Picture plane position

Occlusion

Atmospheric perspective

“depth cueing” in CG

Reduce contrast with distance

Structure from Motion

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Cast Shadows

Stereo Vision Basics

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Right eyeScreen

Left eye

Panum's Fusional Area

disparity = -

Stereopsis

Based on disparities A super acuity Only good near point of fixation Poor for large differences Double imaging possible for 1/10th deg.

Frame Cancellation

Relative Importance

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Cutting, 1996

Depth

Con

trast

Depth (meters)

Occlusion0.001

0.01

0.1

1.0

1 10 100

Relative size

Height in field

Binoculardisparity

Motionparallax

Convergenceaccommodation

Aerial

Task Based Space Perception

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Task Planningand Execution

3D CognitiveModelof Environment

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C2

C3

C4

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C1

C2

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Task Planningand Execution

3D options

Perspective

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Occlusion

MotionParallax

Vergence Focus

Stereopsis

Cue dependencies

Occlusion

Linear Perspective

StereoVergence Kinetic Depth

Texture gradients

Depth of focus

Yes of course 3D can give us moreBut only if it supports some task Locomotion

Heading, occlusion Understanding the shape of surfaces

Shading, texture, stereo, motion Tracing paths in graphs

motion stereo Local reaching

stereo – convergence

Relative position

For fine judgments - threading a needle stereo is important +shadows, occlusion

For large scale judgments, perspective, motion parallax, linear perspective are all important. Stereo is not important

Random Graphs

Glenn looking at a graph

Fish Tank VR

The task

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Number of Nodes

Stereo head coupled perspective

Stereo head coupled perspective2D

2DStereo perspectiveHead coupled perspective

Stereo +60%

Motion +130%

Stereo + Motion+200%

How to generateMotion?

Passive rotation Hand coupled rotation Head-coupled

rotation

Time has does not vary much

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Stereo Display Requirements

3D GIS data Comfortable stereo display Many orders of magnitude Better than normal stereopsis

Stereo Vision Basics

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Right eyeScreen

Left eye

Panum's Fusional Area

disparity = -

We Know That

Vergence and focus conflict Stereo perception is plastic (Wallack) Can be rapidly recalibrated (Judge and

Miles) There is a synergy with motion parallax Occlusion is a strong cue to depth

Cyclopean Scale: (with Cyril Gobrecht)

a

OriginalScaled

Cyclopean Scale Helps with

Vergence focus conflict Diplopia Disparity scaling Frame cancellation It works dynamically? Change the virtual eye separation

Virtual Eye Separation

Change in Eye Separation with Depth

Vir

tual

Eye

Sep

arat

ion

(cm

)

Angle of moving pattern (deg)

10 20 30 40 50 60 70 80468

1012141618202224

Understanding surface shape

Victoria Interrante

Norman, Todd & Phillips

Note: Random textures on surfaces

Stereo and motion roughly equalNote large angular error ~ 20 degrees

Observation: Stereopsis is a super-acuity and relies on fine texture disparity gradients

Conclusion – 3D is better but only it adds something Space perception

depends on the task Occlusion the most

important depth cue – consider that windows rely on it

Perspective may not add anything by itself

Stereo important for close interaction

Motion important for 3D layout

Shape-from shading and texture important for surface perception (but non photorealist)

Stereo technologies

Frame-sequential (shutter glasses) Polaroids Mirror stereoscope HMDs Color anaglyphs Chromadepth

Holograms

Stereo shutter glassesAlternate right and left eye images on monitor. Syncronized shutters block right and left eyes in alternation

Monitor: 120 HzR,L eyes 60 Hz each

Problems: ghosting due to slowPhosphor decay.Lower resolutionCRT displays onlyExpensive glasses

Polaroids

R

L

Silver screenPreserves polarization

Problems:ghosting

Advantages: Cheap glasses

Anaglyphs

Problems:GhostingInability to use color

Lenticular

To Right EyeTo Left Eye

The display uses cylindricalPrisms in vertical columns

Problems: reduced resolution, limited head position.Theoretical limits on resolution

What is wrong with this picture?

Works with LCD displays

Mirror stereoscope

Advantages: no ghostingRetains full brightnessFull spatiotemporal resolution possible

Disadvantage: Fixed head position.

HMD stereoscope

Different screens for each eye.

A high image quality is possible, but not currently available

VR

What is it? What is it for? Perception/interaction

Issue

Resolution Ghosting Vergence-focus conflict Occlusion Crossed disparities

Immersion VR

HMD + head tracking Data glove

Fish Tank VR Head tracking, stereo, touch

Desk Top VR

Interactive 3D

CAVE

Head tracking – stereo Resolution problems Light scattering problems Vergence focus problem for near object Occlusion problems for near objects

Data walls (near immersion) Stereo, no head tracking, wide screen

Immersadesk

Head tracking, stereo

Augmented reality (Feiner) Add text+images to real world See through glasses Very sensitive to head tracking Occlusion problems