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Early Days

Early Days. Generic Computer Graphics Configuration The Display Point Plotting Displays Refresh CRTs Phosphors Display Processor. Generic Computer Graphics Configuration. Terminal. other input. general purpose computer. Computer. Image Description. user view. Display Processor.

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Early Days

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  1. Early Days Generic Computer Graphics Configuration The Display Point Plotting Displays Refresh CRTs Phosphors Display Processor CS 770 – Early Days Lecture 1

  2. Generic Computer Graphics Configuration Terminal other input general purpose computer Computer Image Description user view Display Processor Display Device Display CS 770 – Early Days Lecture 1

  3. The Display y y Beware: x x y x Cartesian Grid of Pixels (mutually exclusive? overlapping blobs?) Addressable (x,y), Small Area (not “points”) Contains a value I(x,y) – brightness/density, color(?), arbitrary code Cameras sense I(x,y) Programs specify I(x,y) (see “Image Description”) CS 770 – Early Days Lecture 1

  4. Point Plotting Displays Image Description Series of x,y pairs Display Processor Reads x,y pairs & treats as command spots&dots quadrille graph paper x-y ink plotter Random Scan CRT BitMap + Raster Scan CRT Questions: how to erase? (new sheet of paper?), how to display? Programmer’s view: Plot(x,y) ClearScreen() CS 770 – Early Days Lecture 1

  5. Refresh CRT focus electron beam electrons deflection phosphor position integrator Direct dx dy x y Points – Move; On, Off Lines - Move; On; Move; Off May go through points we can’t address! See text for Direct View Storage tubes CS 770 – Early Days Lecture 1

  6. Phosphors fluorescence phosphorescence (persistence varies!) So, need a Display Processor Unit (DPU) with a clock...and an instruction pointer... almost a computer! clock Beam Penetration – 2 colors Shadow mask – RGB low light -> high voltage low resolution convergence problems CS 770 – Early Days Lecture 1

  7. DPU Instruction Set Assume “Current Operating Point” (COP) ClearScreen() Moveto(x,y) LineTo(x,y) DrawText(t) MoveRelative(dx,dy) DrawRelative(dx,dy) For refresh, add Addresses and a Stack Jump(a) PushJump(a) PopJump(a) State of the Art...1968 CS 770 – Early Days Lecture 1

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