1. 8/20/2003CS 770 – Early Days Lecture 1 1 Early Days Generic Computer Graphics Configuration The Display Point Plotting Displays Refresh CRTs Phosphors Display Processor

2. 8/20/2003CS 770 – Early Days Lecture 1 2 Generic Computer Graphics Configuration Terminal other input Computer Image Description Display Processor Display Device general purpose computer Display user view

3. 8/20/2003CS 770 – Early Days Lecture 1 3 The Display x y Beware: y x x y 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”)

4. 8/20/2003CS 770 – Early Days Lecture 1 4 Point Plotting Displays xy 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() Pxy C

5. 8/20/2003CS 770 – Early Days Lecture 1 5 Refresh CRT focus deflection electrons electron beam 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

6. 8/20/2003CS 770 – Early Days Lecture 1 6 Phosphors fluorescence phosphorescence (persistence varies!) x y clock So, need a Display Processor Unit (DPU) with a clock...and an instruction pointer... almost a computer! Beam Penetration – 2 colors Shadow mask – RGB low light -> high voltage low resolution convergence problems

7. 8/20/2003CS 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