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Graphics and Human Perception. Presented by: Tumkur Vani, Kanti. What is Perception?. Extraction of information from sensory stimulation.  An active, selective process, influenced by a person's attitude and prior experience.  . Why is Perception important in Graphics?.

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graphics and human perception

Graphics and Human Perception

Presented by:

Tumkur Vani, Kanti

Graphics and Human Perception

what is perception
What is Perception?
  • Extraction of information from sensory stimulation. 
  • An active, selective process, influenced by a person's attitude and prior experience. 

Graphics and Human Perception

why is perception important in graphics
Why is Perception important in Graphics?

Graphics and Human Perception

large variety of advanced electronic imaging equipment

Large variety of advanced electronic imaging equipment

Limiting factor : Need to understand and reactto information displayed and collected by Human Perceptual System

Graphics and Human Perception

psychophysics

Psychophysics

Study of human reactions to physical stimuli or input (EXTERNAL)

Does not explain how or why we react

Graphics and Human Perception

slide6

Design of Imaging devices:Must be closely coupled to human perceptual systemBetter impedance-match between opto-electronics and our neurons

Graphics and Human Perception

in entertainment industry how little information do you need to make the picture look good
In Entertainment industry:“How little information do you need to make the picture look good?”

Graphics and Human Perception

in critical technical analysis using graphics

In critical technical analysis using graphics:

“How much information can we capture and transmit to give the viewer what he or she would see if present at the scene?”

Graphics and Human Perception

weird stuff

Weird stuff

HVS maintains color constancy despite ambient shifts

Extreme sensitivity to spectral (color) differences

No such thing as “static image”!

- Saccadic motion of eyeball

Graphics and Human Perception

slide10

If color can’t be recognized in the first few frames, object will be WIPED from visual memoryCritical in situations like: - Cancer cell detection - Camouflaged tank detection - Subtle motion of an object on a distant planet

Graphics and Human Perception

perceiving our world
Perceiving Our world

Graphics and Human Perception

shadow cues
SHADOW CUES

Graphics and Human Perception

lines and curves
LINES AND CURVES

Graphics and Human Perception

double images
DOUBLE IMAGES

Graphics and Human Perception

impossible figures
IMPOSSIBLE FIGURES

Graphics and Human Perception

slide16

The Brain can be Tricked!!!

Graphics and Human Perception

why is perception important in graphics17

Why is Perception important in Graphics?

Physical accuracy in rendering does not guarantee that the displayed images will have a realistic visual appearance.

Realism

Physically correct,

perceptually equivalent to

the scene

Graphics and Human Perception

how does the eye work
How does the eye work?

Graphics and Human Perception

slide19

Pupil

  • Lens
  • Retina:
    • Protective layer
    • Rods and Cones
    • Bipolar cells
    • Ganglion layer
  • Optic Nerve
  • Light -> electrical nerve impulses

Graphics and Human Perception

spatial awareness stereoscopic vision
Spatial awareness- Stereoscopic vision

Graphics and Human Perception

paradigm shifts

Paradigm shifts

Compression algorithms assume that motion vectors are the most important factor in an imaging system.

IN REALITY: Brain senses the object in the foll sequence:

COLOR, EDGE, MOTION

- If WRONG sequence, then brain does not sense the object at all!

HVS concentrates on selected areas due to:

- SUBLIMINAL cues,

- NOT conscious visual cues

HVS processes sensory input using mechanisms OUTSIDE visual cortex

Graphics and Human Perception

unexpected and counter intuitive data

Unexpected and counter-intuitive data

Important revisions to long-held theories on :

Contrast detection

Temporal and spatial color perception

Motion sensitivity

Object and pattern detection

Visual illusions

Sequencing of subliminal and conscious events

Graphics and Human Perception

design questions

Design Questions

How should color be used?

What graphical entities can be accurately measured?

How many distinct entities can be used without confusion?

What primitives do human detect pre-attentively?

What level of accuracy do we perceive various primitives?

How do we combine primitives to recognize complex phenomena?

Graphics and Human Perception

slide25

Perception-driven rendering algorithms:Ward's contrast-threshold tone reproduction operatorDouglass-Peucker line simplification algorithmPerceptually Based Adaptive Sampling Algorithm - Bolin, M. and G. Meyer Perceptually driven shape simplification algorithm

Graphics and Human Perception

visual function changes dramatically over the range of environmental illumination
Visual function changes dramatically over the range of Environmental Illumination.

Graphics and Human Perception

producing realistic images
Producing Realistic Images

Model :

  • Physical behavior of light propagation
  • Perceptual response parameters

Graphics and Human Perception

tone reproduction operators

Tone Reproduction Operators

Overcome the limits of conventional CRT

displays

Determine how to best display simulated

environments within the

limited dynamic range available.

Graphics and Human Perception

tone reproduction operators29

Tone Reproduction Operators

Preserve the apparent brightness of

scene features

Preserve apparent contrast and visibility

Psychophysical model of glare:

Implements a glare filter that increases

the apparent dynamic range of images.

Graphics and Human Perception

model of adaptation

Model of adaptation

Includes the effects of adaptation on threshold visibility, color appearance, visual acuity, and changes in visual sensitivity over time.

Graphics and Human Perception

visual function across range of light
Visual function across Range of Light

Graphics and Human Perception

applications

Applications

Efficient software ( by not computing those parts of a scene which the human will fail to notice)

Predicting visibility (eg from Cockpit)

Architectural design

Special effects or advertising

Virtual sets in a show

Reconstruction of historic buildings or

places for educational purposes

Graphics and Human Perception

conclusion

Conclusion

Great deal of potential

Images: Perceptually accurate,

Physically correct,

Faithful represenrations

Allows for high level of confidence in

computer-imagery

Graphics and Human Perception

references

References

AS IF YOU WERE THERE : Matching Machine Vision to Human Vision

- Richard Jay Solomon (Univ. of Pennsylvania)

Program on Vision Science & Advanced Networking (2002)

www.hybridvigor.net/human/pubs/index.htm

Perceptually Adaptive Graphics

Ann McNamara and Carol O'Sullivan

- ACM SIGGRAPH AND EUROGRAPHICS CAMPFIRE

http://isg.cs.tcd.ie/campfire (May 26th - 29th, 2001 Snowbird, Utah) http://library.thinkquest.org/C001464/cgi-bin/view.cgi?show_item=perception

Visual Perception in Realistic Image Synthesis

( State of the art (STAR) Report)

- Ann McNamara

Eurographics 2000, Interlaken, Switzerland, August 2000

Graphics and Human Perception

thank you
Thank You

Graphics and Human Perception