cornell cs465 fall 2004 lecture 2© 2004 steve marschner 1 displays
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© 2004 Steve Marschner • 1Cornell CS465 Fall 2004 • Lecture 2
Displays
© 2004 Steve Marschner • 2Cornell CS465 Fall 2004 • Lecture 2
Framebuffer
[From Talton]
© 2004 Steve Marschner • 3Cornell CS465 Fall 2004 • Lecture 2
Cathode ray tube (CRT)
• First widely used electronic display– developed for TV in the 1920s–1930s
[H&
B fi
g.
2-2
]
© 2004 Steve Marschner • 4Cornell CS465 Fall 2004 • Lecture 2
Raster CRT display
• Intensity modulated to produce image• Originally for TV
– (continuous analog signal)
[H&
B fi
g.
2-7
]
© 2004 Steve Marschner • 5Cornell CS465 Fall 2004 • Lecture 2
CRT refresh images
© 2004 Steve Marschner • 6Cornell CS465 Fall 2004 • Lecture 2
Interlacing vs progressive scan
© 2004 Steve Marschner • 7Cornell CS465 Fall 2004 • Lecture 2
Interlacing vs progressive scan
© 2004 Steve Marschner • 8Cornell CS465 Fall 2004 • Lecture 2
Interlacing vs progressive scan
© 2004 Steve Marschner • 9Cornell CS465 Fall 2004 • Lecture 2
Vector vs raster scan
Arthur Clokey, the creator of Gumby, trying out NYIT CGL'sBBOP 3D keyframe animation system using an E & S vector display, 1984. Tempest
© 2004 Steve Marschner • 10Cornell CS465 Fall 2004 • Lecture 2
LCD flat panel or projection display• Principle: block or transmit light by twisting its polarization• Intermediate intensity
levels possible bypartial twist
• Fundamentally rastertechnology
[H&
B fi
g.
2-1
6]
© 2004 Steve Marschner • 11Cornell CS465 Fall 2004 • Lecture 2
LCD
© 2004 Steve Marschner • 12Cornell CS465 Fall 2004 • Lecture 2
Color displays
• Humans are trichromatic– match any color
with blend of three
• Additive color– blend images by sum– R, G, B make good primaries
[cs4
17
S0
2 s
lides]
red blue
green
yellow cyan
magenta
white
© 2004 Steve Marschner • 13Cornell CS465 Fall 2004 • Lecture 2
Color displays
• CRT: phosphor dot pattern to produce finely interleaved color images
• LCD: interleaved R,G,B pixels [H&
B fi
g.
2-1
0]
© 2004 Steve Marschner • 14Cornell CS465 Fall 2004 • Lecture 2
Triads and color mixing
SMPTE color bars
closeup on a Sony Trinitron monitor
Slide from Marc Levoy
© 2004 Steve Marschner • 16Cornell CS465 Fall 2004 • Lecture 2
DLP
© 2004 Steve Marschner • 17Cornell CS465 Fall 2004 • Lecture 2
Triads versus pixels
antialiased font(Adobe Acrobat)
subpixel font(Adobe Cooltype)
integral pixel font(IBM LCD)
integral pixel font(Sony Trinitron)
Slide from Marc Levoy
Kindle iPad
http://www.bit-101.com/blog/?p=2722
At 26x
Kindle iPad
http://www.bit-101.com/blog/?p=2722
At 400x
NewsPrint
http://www.bit-101.com/blog/?p=2722
© 2004 Steve Marschner • 25Cornell CS465 Fall 2004 • Lecture 2
How much spatial resolution (pixels) do we need?
© 2004 Steve Marschner • 26Cornell CS465 Fall 2004 • Lecture 2
How much temporal resolution (frames per second) do we need?
dark
bright
(fps)
© 2004 Steve Marschner • 27Cornell CS465 Fall 2004 • Lecture 2
Transfer function of display
• Say pixel value is 123– this means the intensity is 123. 123 what?
100%
00 255
like this?
(voltage)(frame buffer value)
(light)(photons)
© 2004 Steve Marschner • 28Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 29Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 30Cornell CS465 Fall 2004 • Lecture 2
Why nonlinear intensity?
~0.000.010.040.090.160.250.360.490.640.811.00
~0.00.10.20.30.40.50.60.70.80.91.0
• Closer to ideal perceptually uniform exponential
© 2004 Steve Marschner • 31Cornell CS465 Fall 2004 • Lecture 2
Checkerboard test
n = 64
n = 128
n = 192
I = 0.25 I = 0.5 I = 0.75
© 2004 Steve Marschner • 32Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 33Cornell CS465 Fall 2004 • Lecture 2
Gamma correction
[Phili
p G
reensp
un]
OKcorrected forg lower than
display
corrected forg higher than
display
© 2004 Steve Marschner • 34Cornell CS465 Fall 2004 • Lecture 2
8 bpp (256 grays)7 bpp (128 grays)6 bpp (64 grays)5 bpp (32 grays)4 bpp (16 grays)3 bpp (8 grays)2 bpp (4 grays)1 bpp (2 grays)
Quantization
[Phili
p G
reensp
un]
© 2004 Steve Marschner • 35Cornell CS465 Fall 2004 • Lecture 2
• 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?)
© 2004 Steve Marschner • 36Cornell CS465 Fall 2004 • Lecture 2
Ordered dither example
• Produces regular grid of compact dots
[Phili
p G
reensp
un]
© 2004 Steve Marschner • 37Cornell CS465 Fall 2004 • Lecture 2
Diffusion dither
• Produces scattered dots with the right local density
[Phili
p G
reensp
un]
© 2004 Steve Marschner • 38Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 39Cornell CS465 Fall 2004 • Lecture 2
© 2004 Steve Marschner • 40Cornell CS465 Fall 2004 • Lecture 2
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