Imagery CS 110 Fall 2005. Image Technology Always Changing Paint / pencil Paint / pencil Cave...
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Transcript of Imagery CS 110 Fall 2005. Image Technology Always Changing Paint / pencil Paint / pencil Cave...
ImageryImagery
CS 110CS 110
Fall 2005Fall 2005
Image Technology Always Image Technology Always ChangingChanging
Paint / pencilPaint / pencil• Cave drawingsCave drawings• Perspective renditionsPerspective renditions• ImpressionismImpressionism
OpticsOptics• Photographs Photographs • Photo volumes that shift lighting, time, Photo volumes that shift lighting, time,
and spaceand space
Early Imagery: In the Mind’s Early Imagery: In the Mind’s EyeEye
Improving Improving ImageryImagery
Equations dictateEquations dictateimage image
Mastering PerspectiveMastering PerspectiveLorenzetti (1342)Lorenzetti (1342)
Rules for a New EraRules for a New Era
PhotorealismPhotorealism
Perspective, therefore, should be Perspective, therefore, should be preferred above all man’s discourses preferred above all man’s discourses and disciplines. and disciplines. (Da Vinci, 1400)(Da Vinci, 1400)
Image Generation TechnologyImage Generation Technology
Camera ObscuraCamera Obscura• 1515thth Century Century
Camera’s Inhibit Art?Camera’s Inhibit Art?
There are some who… trace outlines on a There are some who… trace outlines on a surface of a transparent medium.surface of a transparent medium.
Such an invention is to be condemned in Such an invention is to be condemned in those who do not know how to portray those who do not know how to portray things without it, nor how to reason about things without it, nor how to reason about nature with their mind.nature with their mind.
They are always poor and mean in every They are always poor and mean in every invention and in the invention and in the composition of composition of narrativesnarratives, which is the final aim of this , which is the final aim of this science.science.
(Da Vinci)
Can a Camera do This?Can a Camera do This?
Artistic controlArtistic controlof vanishingof vanishingpointpoint
(Da Vinci, 1498)
Can a Camera do This?Can a Camera do This?
Yes!Yes!
We’ll discussWe’ll discussexciting newexciting newtechnologiestechnologies
(Da Vinci, 1498)
Photographs vs. MomentsPhotographs vs. Moments PhotographPhotograph: an (almost : an (almost objectiveobjective) )
representation of a point in time and representation of a point in time and spacespace
MomentMoment: a visual representation of the : a visual representation of the subjectivesubjective reality at some time and place reality at some time and place
From M. Cohen, Microsoft Researchhttp://research.microsoft.com/~cohen/TheMoment.pdfhttp://research.microsoft.com/~cohen/FindingMagicInAnImageStack.pdf
Photographs vs. MomentsPhotographs vs. Moments
Artists capture moments so wellArtists capture moments so well
Photographs vs. MomentsPhotographs vs. Moments
With introduction of cameras, art With introduction of cameras, art became more abstract (to became more abstract (to compensate)compensate)
Have cameras lost the moment?Have cameras lost the moment? Can we recapture it?Can we recapture it?
Some InspirationSome Inspiration
The old days: 35mm film, $0.30 / picThe old days: 35mm film, $0.30 / pic Now: DigitalNow: Digital
• Disk storage = $1 / GigabyteDisk storage = $1 / Gigabyte• DVD = $0.50 / GigabyteDVD = $0.50 / Gigabyte• Images =~ 1 MbyteImages =~ 1 Mbyte
• 1 picture < $0.001 =~ free1 picture < $0.001 =~ free
From M. CohenMicrosoft Research
PhotosPhotos
Our roots: Edison’s 35mm film (1889)Our roots: Edison’s 35mm film (1889)
• Chemical coatingChemical coatingreacts to lightreacts to light
• Specific chemicalsSpecific chemicalsreact to uniquereact to uniquewavelengthswavelengths
Analog recording of visible wavelengths and intensities (continuous data)
ImagesImages
An image is a 2D function An image is a 2D function II(x, y) that (x, y) that specifies intensity for each point (x, specifies intensity for each point (x, y)y)
From L. McMillanMIT Comp. Graphics
Analog to DigitalAnalog to Digital
Our goal is to convert the continuous Our goal is to convert the continuous image to a discrete set of samplesimage to a discrete set of samples
Point Sampling an ImagePoint Sampling an Image
Simplest sampling is on a gridSimplest sampling is on a grid Sample dependsSample depends
solely on valuesolely on valueat grid pointsat grid points
Point SamplingPoint Sampling
Multiply sample grid by image Multiply sample grid by image intensity to obtain a discrete set of intensity to obtain a discrete set of points, or points, or samples.samples.
A to D, 2-D ExampleA to D, 2-D Example
Analog to digital conversionAnalog to digital conversion
location on image slice
inte
nsi
ty
Analog Signal
image slice
A to D, 2-D ExampleA to D, 2-D Example
Analog to digital conversionAnalog to digital conversion
location on image slice
inte
nsi
ty
Analog Signal
image slice
location on image slice
inte
nsi
ty
samples
Digital Signal
From Computer Graphics: Principles and Practice
Sensor ArraysSensor Arrays
Capturing “samples” of lightCapturing “samples” of light
Sensor ArraysSensor Arrays
Storing amount of light contacting Storing amount of light contacting squares on a surfacesquares on a surface• Each square tuned toEach square tuned to
sense red, green, or bluesense red, green, or blue• More green squares thanMore green squares than
othersothers• Humans see green bestHumans see green best
(lots of tigers in the grass)(lots of tigers in the grass)
Human PerceptionHuman Perception
We see these colors (mostly green)We see these colors (mostly green)
Sensor ArraysSensor Arrays
Very smallVery small Lenses focus lightLenses focus light Light generates Light generates
electricity that is electricity that is sensed by a silicon sensed by a silicon chipchip
Sensor ArraysSensor Arrays
Pixel: each square in sensor arraysPixel: each square in sensor arrays Resolution: number of pixelsResolution: number of pixels Color depth: number of bits that Color depth: number of bits that
describe the “reading” at each pixeldescribe the “reading” at each pixel
Sensor ArraysSensor Arrays
Aliasing: a common problem when Aliasing: a common problem when discretizing analog datadiscretizing analog data
Moire Pattern
Sensor ArraysSensor Arrays
Noise: at low light, small errors in Noise: at low light, small errors in pixel “readings” are very apparentpixel “readings” are very apparent• Human perception is more sensitive to Human perception is more sensitive to
small errors at low intensitiessmall errors at low intensities
Digital cameras have more trouble Digital cameras have more trouble than film cameras in low lightthan film cameras in low light
CompressionCompression
Light intensity at all sensors can be Light intensity at all sensors can be recordedrecorded• Large: RAW and TIFF file formatsLarge: RAW and TIFF file formats
Small, local intensity variations can Small, local intensity variations can be lumped togetherbe lumped together• JPEG (most common of digital cameras)JPEG (most common of digital cameras)• GIF (common web format)GIF (common web format)
Digital to AnalogDigital to Analog
New Display TechnologiesNew Display Technologies
Display WallsDisplay Walls• PrincetonPrinceton• StanfordStanford• UVa – Greg UVa – Greg
HumphreysHumphreys
Interesting Display Interesting Display TechnologiesTechnologies
Wood chips Chrome spheresWood chips Chrome spheres
Daniel Rozin – NYU: (movies) http://fargo.itp.tsoa.nyu.edu/~danny/art.html
Human PerceptionHuman Perception
A monitor can display these colorsA monitor can display these colors• Note how limitingNote how limiting
they arethey are
Human PerceptionHuman Perception A photograph is a poor A photograph is a poor
model of realistic lighting model of realistic lighting conditionsconditions• Cannot convey shadows Cannot convey shadows
and bright spots of real and bright spots of real scenesscenes
• Artists use optical illusions Artists use optical illusions to fool us into sensing to fool us into sensing lighting conditionslighting conditions
Photographers have Photographers have limited abilities to limited abilities to replicate artistic featuresreplicate artistic features
Jack Tumblin, SIGGRAPH ‘99
Creating MomentsCreating Moments
Automatically capitalizing on artistic Automatically capitalizing on artistic techniques to emphasize photostechniques to emphasize photos
Creating interactive photo Creating interactive photo techniquestechniques
Modern TechnologyModern TechnologyStanford
New ResultsNew Results
Ng – Stanfordhttp://graphics.stanford.edu/papers/lfcamera/
New ResultsNew Results
Ng - Stanford
New ResultsNew Results
http://graphics.stanford.edu/papers/http://graphics.stanford.edu/papers/lfcamera/lfcamera.wmvlfcamera/lfcamera.wmv
Modern TechnologyModern Technology
Mitsubishi Electric Research Labs
New ResultsNew Results
Artist Rendition
MERL Cam
Shadows indicate edgesShadows indicate edges
New ResultsNew Results
New ResultsNew Results
http://www.merl.com/people/raskar/http://www.merl.com/people/raskar/NprCamera/nprMovie320short2.aviNprCamera/nprMovie320short2.avi
New ResultsNew Results
Multi-ExposureMulti-Exposure
Durand - MIT
New ResultsNew Results
M. CohenMicrosoft Research
New ResultsNew Results
Automatic PanoramasAutomatic Panoramas
M. CohenMicrosoft Research
Modern TechnologyModern Technology
10 Mpixel Sensor10 Mpixel Sensor 200 fps200 fps Buffers 5 seconds of captureBuffers 5 seconds of capture
• 10 Gigapixel circular buffer10 Gigapixel circular buffer• Continuously “on” Continuously “on”
M. CohenMicrosoft Research
Merge Multiple ShotsMerge Multiple Shots
New Display TechnologiesNew Display Technologies
Light StageLight Stage
New Display TechnologiesNew Display Technologies
http://gl.ict.usc.edu/research/LS5/http://gl.ict.usc.edu/research/LS5/LS5_Siggraph_052005.aviLS5_Siggraph_052005.avi