Displays
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 1
Framebuffer
Cornell CS465 Fall 2004 • Lecture 2
[From Talton]
© 2004 Steve Marschner • 2
Cathode ray tube (CRT)
• First widely used electronic display
[H&B fig. 2-2]
– developed for TV in the 1920s–1930s
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 3
Raster CRT display
• Intensity modulated to produce image
• Originally for TV
[H&B fig. 2-7]
– (continuous
analog signal)
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 4
CRT refresh images
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 5
Interlacing vs progressive scan
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 6
Interlacing vs progressive scan
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 7
Interlacing vs progressive scan
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 8
Vector vs raster scan
Arthur Clokey, the creator of Gumby, trying out NYIT CGL's
BBOP 3D keyframe animation system using an E & S vector display, 1984.
Cornell CS465 Fall 2004 • Lecture 2
Tempest
© 2004 Steve Marschner • 9
• Principle: block or transmit light by twisting its polarization
• Intermediate intensity
levels possible by
partial twist
• Fundamentally raster
technology
Cornell CS465 Fall 2004 • Lecture 2
[H&B fig. 2-16]
LCD flat panel or projection display
© 2004 Steve Marschner • 10
LCD
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 11
Color displays
• Humans are trichromatic
– match any color
with blend of three
• Additive color
– blend images by sum
– R, G, B make good primaries
green
yellow
red
cyan
white
blue
[cs417 S02 slides]
magenta
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 12
Color displays
• LCD: interleaved R,G,B pixels
Cornell CS465 Fall 2004 • Lecture 2
[H&B fig. 2-10]
• CRT: phosphor dot pattern to produce finely interleaved color images
© 2004 Steve Marschner • 13
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 14
Triads and color mixing
SMPTE color bars
closeup on a Sony Trinitron monitor
Slide from Marc Levoy
DLP
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 16
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 17
Triads versus pixels
integral pixel font
integral pixel font
antialiased font
subpixel font
(Sony Trinitron)
(IBM LCD)
(Adobe Acrobat)
(Adobe Cooltype)
Slide from Marc Levoy
Kindle
At 26x
iPad
http://www.bit-101.com/blog/?p=2722
Kindle
At 400x
iPad
http://www.bit-101.com/blog/?p=2722
NewsPrint
http://www.bit-101.com/blog/?p=2722
How much spatial resolution (pixels) do we need?
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 25
How much temporal resolution (frames per second) do we need?
bright
dark
(fps)
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 26
Transfer function of display
• Say pixel value is 123
– this means the intensity is 123. 123 what?
100%
like this?
(light)
(photons)
0
0
Cornell CS465 Fall 2004 • Lecture 2
(voltage)
(frame buffer value)
255
© 2004 Steve Marschner • 27
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 28
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 29
Why nonlinear intensity?
~0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
~0.00
0.01
0.04
0.09
0.16
0.25
0.36
0.49
0.64
0.81
1.00
• Closer to ideal perceptually uniform exponential
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 30
Checkerboard test
n = 64
n = 128
n = 192
I = 0.25
Cornell CS465 Fall 2004 • Lecture 2
I = 0.5
I = 0.75
© 2004 Steve Marschner • 31
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 32
[Philip Greenspun]
Gamma correction
corrected for
g lower than
display
Cornell CS465 Fall 2004 • Lecture 2
OK
corrected for
g higher than
display
© 2004 Steve Marschner • 33
8 bpp
(256
grays)
7 bpp
(128
6 bpp
(64grays)
grays)
5 bpp
(32
grays)
4 bpp
(16
3 bpp
(8grays)
grays)
2 bpp
(4
grays)
1 bpp
(2
grays)
Cornell CS465 Fall 2004 • Lecture 2
[Philip Greenspun]
Quantization
© 2004 Steve Marschner • 34
• You make a black and white printer.You
don’t want your pictures to come out
like this. Design a system for converting
grayscale images to black/white that will
look better than this. (You can only use
black/white, what value goes in each
pixel?)
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 35
Ordered dither example
[Philip Greenspun]
• Produces regular grid of compact dots
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 36
Diffusion dither
Produces scattered dots with the right local density
[Philip Greenspun]
•
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 37
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 38
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 39
Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 40