Basics of a
Computer Graphics System
Introduction to Computer Graphics
CSE 470/598
Arizona State University
Dianne Hansford
Elements
Input Devices
keyboard, mouse
Processor
Memory
rasterization:
geometry to pixels
Frame Buffer
pixels live here,
VRAM, DRAM memory
Output Devices
CRT (cathode-ray tube)
Frame Buffer (FB)
 A picture is produced by an n x m array of pixels
(picture elements)
 Also known as raster
 Pixels live in memory called the frame buffer.
 Fast re-display of FB implemented with special
memory: DRAM, VRAM
Frame Buffer Depth
Depth: number of bits for each pixel
 number of colors represented
1 bit = 2 colors (black and white)
8 bit = 2^8 = 256 colors
16 bit = “high color”
Color index mode
Color map
24 bit = 16M colors “full color” or “true color”
32 bit = a lot!
RGB color
RGB Color
Primary colors: red, green, blue
In each pixel,
individual bits assigned to each color
24 bit  8 bits R,
8 bits G,
8 bits B
RGB Color Scheme
Frame Buffer Resolution
Resolution: number of pixels
640 x 480 ≈ 300K pixels
1024 x 768 ≈ 780K pixels
1600 x 1200 ≈ 2M pixels
color buffer
depth buffer
buffer 
data stored uniformly
for each pixel
fragments = pre-FB rasterization info, correspond to pixels,
color and depth
Output Device: Raster System
 Pixels from FB displayed as points on CRT
 CRT: electrons strike phosphor and light is emitted and
directed toward screen
3 phosphors: RGB
 Light emitted a short time (milliseconds)  must refresh
 Common: refresh at 60-80 Hz (times per second)
 Other rasters: LCD, plasma, digital projection, …