Graphics and Human Perception Presented by: Tumkur Vani, Kanti 9/18/2018 Graphics and Human Perception

Graphics and Human Perception What is Perception? Extraction of information from sensory stimulation.  An active, selective process, influenced by a person's attitude and prior experience.  9/18/2018 Graphics and Human Perception

Why is Perception important in Graphics? 9/18/2018 Graphics and Human Perception

Large variety of advanced electronic imaging equipment Limiting factor : Need to understand and react to information displayed and collected by Human Perceptual System 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Psychophysics Study of human reactions to physical stimuli or input (EXTERNAL) Does not explain how or why we react 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Design of Imaging devices: Must be closely coupled to human perceptual system Better impedance-match between opto-electronics and our neurons 9/18/2018 Graphics and Human Perception

Graphics and Human Perception In Entertainment industry: “How little information do you need to make the picture look good?” 9/18/2018 Graphics and Human Perception

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?” 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 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 9/18/2018 Graphics and Human Perception

Graphics and Human Perception If color can’t be recognized in the first few frames, object will be WIPED from visual memory Critical in situations like: - Cancer cell detection - Camouflaged tank detection - Subtle motion of an object on a distant planet 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Perceiving Our world 9/18/2018 Graphics and Human Perception

Graphics and Human Perception SHADOW CUES 9/18/2018 Graphics and Human Perception

Graphics and Human Perception LINES AND CURVES 9/18/2018 Graphics and Human Perception

Graphics and Human Perception DOUBLE IMAGES 9/18/2018 Graphics and Human Perception

Graphics and Human Perception IMPOSSIBLE FIGURES 9/18/2018 Graphics and Human Perception

Graphics and Human Perception The Brain can be Tricked!!! 9/18/2018 Graphics and Human Perception

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 9/18/2018 Graphics and Human Perception

Graphics and Human Perception How does the eye work? 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Pupil Lens Retina: Protective layer Rods and Cones Bipolar cells Ganglion layer Optic Nerve Light -> electrical nerve impulses 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 9/18/2018 Graphics and Human Perception

Spatial awareness - Stereoscopic vision 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 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 9/18/2018 Graphics and Human Perception

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 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 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? 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Perception-driven rendering algorithms: Ward's contrast-threshold tone reproduction operator Douglass-Peucker line simplification algorithm Perceptually Based Adaptive Sampling Algorithm - Bolin, M. and G. Meyer Perceptually driven shape simplification algorithm 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Visual function changes dramatically over the range of Environmental Illumination. 9/18/2018 Graphics and Human Perception

Producing Realistic Images Model : Physical behavior of light propagation Perceptual response parameters 9/18/2018 Graphics and Human Perception

Tone Reproduction Operators Overcome the limits of conventional CRT displays Determine how to best display simulated environments within the limited dynamic range available. 9/18/2018 Graphics and Human Perception

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. 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Model of adaptation Includes the effects of adaptation on threshold visibility, color appearance, visual acuity, and changes in visual sensitivity over time. 9/18/2018 Graphics and Human Perception

Visual function across Range of Light 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 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 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Conclusion Great deal of potential Images: Perceptually accurate, Physically correct, Faithful represenrations Allows for high level of confidence in computer-imagery 9/18/2018 Graphics and Human Perception

Graphics and Human Perception 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 9/18/2018 Graphics and Human Perception

Graphics and Human Perception Thank You 9/18/2018 Graphics and Human Perception