LIBRI (cid:5) 3D Computer Graphics, Alan Watt, Second Edition, Addison-Wesley, 1993 (cid:5) Computer Graphics: Principles and Practice (Second Edition in C), J. Foley, A. Van Dam, S. Feiner, and J. Hughes, Addison-Welsey, 1995 1 History Advantages of Computer graphics: (cid:5) Used in many application and research domains: Interactivity Interactive plotting CAD O(cid:14)ce automation Scienti(cid:12)c visualization Animation - entertainment Art - advertising Process control Cartography Medicine 1 History History (cid:5) Early 60’s: Early graphics dominated by (cheap) storage tube technology (eg. Tektronix) (cid:5) Bu(cid:11)er memory and processor fast enough to refresh at, at least, 30 Hz were −! expensive flickering (cid:5) Late 60’s: Introduction to direct view storage tube (DVST) that stores the image −! no more flickering Display process attached to a −! minicomputer relief for the central unit 2 History (cid:5) Early 70’s: Vector CRT developed from established oscilloscope technology (CRT: Cathode Ray Tube) (cid:5) Mid 70’s: Raster graphics became feasible as memory cost drop (cid:5) Introduction of raster displays: Inexpensive 3 History (cid:5) A raster is a rectangular array of points or dots called \pixels". (cid:5) A row of pixels is called a \scan line". (cid:5) Raster images are displayed by drawing the pixels sequentially in a (cid:12)xed order. (cid:5) Colors are created by separately exciting Red, Green, Blue phosphors inside the CRT imaging device. 4 History (Raster displays store display primitives (line, characters, patterned areas, solid shared areas) in a refresh bu(cid:11)er in terms of their component pixels) (cid:5) Image on a raster: Set of raster lines (horizontal), each row of individual pixels. −! Stored as a matrix of pixels representing the entire screen area. 5 History Raster Graphics De(cid:12)nitions (cid:5) Spatial resolution: elements * scan lines e.g. 5 x 5 (cid:5) Intensity or color resolution - 2depth eg. here, each pixel can have any of 16 values 6 History 5 scan lines 5 elements 5 scan lines 3 depth 5 elements 7 History (cid:5) Advantages of raster devices over vector devices: Lower cost and ability to display (cid:12)lled area (cid:5) Disadvantage: Each primitive must be scan-converted e.g. vector is de(cid:12)ned by its end points. To be displayed on a raster device −! need scan conversion Pb of anti-aliasing 8 History Frame Bu(cid:11)er Architectures (cid:5) Most computer (or special-purpose hardware) transmits command and data across an interface (cid:5) The raster image described by this data is stored in a \frame bu(cid:11)er" memory. (cid:5) The frame bu(cid:11)er is built from one or more \bit planes" - 2D arrays of bits. This memory can be peripheral to the host or resident as part of the host computer’s address space, and therefore referenced directly. 9