INTRODUCTION
Applied Perception for Visual Computing
Jehee Lee
A lot of slides stolen from Aditi Majumder
Instructors
• Carol O’Sullivan
• Professor, Trinity College Dublin
• Sabbatical visit at SNU starting from Oct 2012
• Computer graphics, Computer animation, Human
perception, Eye movements
• Office/Phone will be available soon
• Jehee Lee
• Professor, Seoul National University
• Computer graphics, Computer animation, Human
movements, Biomechanics, Robotics
• Office: 302-325
• Phone: 1845
Course Introduction
• Understanding and applying principles of human
perception
• We are particularly interested in visual computing
• Computer graphics, computer vision, virtual reality, image
processing, visualization, experimental psychology, neuroscience
• Access and enhance computer-generated scenes,
animations, and virtual environments.
• The course will be delivered via a combination of lectures,
guest speakers, and student presentations
Recommended references
• Visual Perception from a Computer Graphics
Perspective, W. B. Thompson, R. W. Fleming,
S. H. Creem-Regehr, J. K. Stefanucci, CRC
Press.
• Vision and Art: The Biology of Seeing,
Margaret Livingstone, Abrams.
Grading Policy
• Course participation, presentation: 50%
• Term project or term paper: 50%
What is Perception?
• Sensory experience of the world around us
• Involves
• Recognition of environmental stimuli
• Actions in response to these stimuli
• Five senses: touch, sight, smell, taste, hear
• Proprioception
• A set of senses involving the ability to detect changes in body
positions and movements
You are easily fooled
Perceptual Process
• Cycles of Environment, Perception, and Action
• Continual
• You do not spend much time thinking about the actual process
• Unconscious, Automatic
• Eg) Transforming light on your retinas into visual image
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Environmental Stimulus
• Anything in our environment that we can perceive
• Can be anything we can sense
• see, hear, touch, smell, taste, or
• the sense of proprioception
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Attended Stimulus
• A part of the environmental stimulus
• Focuses attention on this stimulus
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Stimulus on receptors
• The attended stimuli excites the receptors
• For example
• Visual stimulus formed as an image on the retina
• Sound changes pressure to affect the ear drum
• Note
• We do not perceive the image on the retina
• It is just one of the initial steps of the process
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Transduction
• Transformation of one form of energy to other
• Environmental energy transformed to electrical energy
• The image on the retina generates electrical signals in the
tens and thousands receptors of the eye
Photoreceptor cells
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Neural processing
• Neurons are elements of nervous system
• Interconnected together
• Processing of the electrical energy by the neurons while
they travel through them
• This changes the electrical energy in various ways
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Perception
• Conscious sensory experience
• Electric energy transforms in brain to some experience
• Is this the end of perception?
• Recognition and action are important outcomes of the perceptual
process
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Recognition
• Identifying the experience as something
• Known
• Similar to some experience before
• Placing objects in meaningful categories
• Recognition and Perception are two separate process
• The Man who Mistook his Wife for a Hat
• By Oliver Sacks
• The case study of a man with visual agnosia
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Action
• Goal of perception is to create action
• Evolutionary reason for development of perception
• Motor activities
• It can be a major action, like running toward the subject
• It can be as subtle as blinking eyes
• Response to perception and recognition
• Leads to
• New attended stimulus
• Whole cycle repeats
Perceptual Process
Perception
Knowledge
Recognition
Processing
Action
Transduction
Environment Stimulus
Stimulus on Receptors
Attended Stimulus
Knowledge
• Affects
• Processing, Perception, Recognition
• Identification from memory
• Old knowledge
• Recent knowledge
Cognitive Influences on Perception
Cognitive Influences on Perception
Cognitive Influences on Perception
Cognitive Influences on Perception
Gestalt Psychology
• Gestalt (German)
• Essence or shape of an entity’s complete form
• A theory of mind and brain
• Gestalt psychologists stipulate that perception is the
product of complex interactions among various stimuli
• The whole is different than the sum of its parts
• Contrary to the behaviorist approach to understanding the elements
of cognitive processes
• There are principles (or heuristics) often referred to as the
“laws of perceptual organizations”
Images taken from http://psychology.about.com/
Images taken from http://psychology.about.com/
Images taken from http://psychology.about.com/