Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 1 Displays

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 2 Framebuffer [From Talton]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 3 Cathode ray tube (CRT) First widely used electronic display –developed for TV in the 1920s–1930s [H&B fig. 2-2]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 4 Raster CRT display Intensity modulated to produce image Originally for TV –(continuous analog signal) [H&B fig. 2-7]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 5 CRT refresh images

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 Interlacing vs progressive scan

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 9 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, Tempest

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 10 LCD flat panel or projection display Principle: block or transmit light by twisting its polarization Intermediate intensity levels possible by partial twist Fundamentally raster technology [H&B fig. 2-16]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 11 LCD

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 12 Color displays Humans are trichromatic –match any color with blend of three Additive color –blend images by sum –R, G, B make good primaries [cs417 S02 slides] redblue green yellowcyan magenta white

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 13 Color displays CRT: phosphor dot pattern to produce finely interleaved color images LCD: interleaved R,G,B pixels [H&B fig. 2-10]

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

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 16 DLP

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 17

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

KindleiPad At 26x

KindleiPad At 400x

NewsPrint

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 24

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 25 How much spatial resolution (pixels) do we need?

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 26 How much temporal resolution (frames per second) do we need? dark bright (fps)

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 27 Transfer function of display Say pixel value is 123 –this means the intensity is what? 100% like this? (voltage) (frame buffer value) (light) (photons)

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Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 29

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 30 Why nonlinear intensity? ~ ~ Closer to ideal perceptually uniform exponential

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 31 Checkerboard test n = 64 n = 128 n = 192 I = 0.25I = 0.5I = 0.75

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Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 33 Gamma correction [Philip Greenspun] OKcorrected for g lower than display corrected for g higher than display

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 34 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 [Philip Greenspun]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 35 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 36 Ordered dither example Produces regular grid of compact dots [Philip Greenspun]

Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 37 Diffusion dither Produces scattered dots with the right local density [Philip Greenspun]

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Cornell CS465 Fall 2004 Lecture 2© 2004 Steve Marschner 39

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