1. Basics of a Computer Graphics System Introduction to Computer Graphics CSE 470/598 Arizona State University Dianne Hansford

2. Elements Input Devices Processor Memory Frame Buffer Output Devices keyboard, mouse CRT (cathode-ray tube) pixels live here, VRAM, DRAM memory rasterization: geometry to pixels

3. 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

4. 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” 24 bit = 16M colors “full color” or “true color” 32 bit = a lot! RGB color Color index mode Color map

5. 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

6. RGB Color Scheme

7. 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

8. 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, …