Graphics Hardware Cathode Ray Tube (CRT) 1 2 3 4 5 6 Monitor (CRT, LCD,…) Graphics accelerator Scan controller Video Memory (frame buffer) 1. Filament (generate heat) Display/Graphics Processor 2. Cathode (emit electrons) CPU/Memory/Disk … 3. Control grid (control intensity) 4. Focus 5. Deflector 6. Phosphor coating Color CRT LED 3 electron guns, 3 color phosphor dots at each pixel Color = (red, green, blue) Black = (0,0,0) White = (1,1,1) Red = 0 to 100% Red = (1,0,0) Green = 0 to 100% Green = (0,1,0) Blue = 0 to 100% Blue = (0,0,1) … 1 LCD Plasma Panels Raster Display graphics How to draw a picture? Digital Display Based on (analog) raster-scan TV technology The screen (and a picture) consists of discrete pixels, and each pixel has one or multiple phosphor dots We have only one electron gun but many pixels in a picture need to be lit simultaneously… 2 Refresh Random Scan Order Refresh – the electron gun needs to come back to Old way: No pixels - The electron gun hit the pixel again before it fades out draws straight lines from location to An appropriate fresh rate depends on the property of location on the screen (vector graphics) phosphor coating Phosphor persistence: the time it takes for the a.k.a. calligraphic display, emitted light to decay to 1/10 of the original intensity Random scan device, vector drawing display Typical refresh rate: 60 – 80 times per second (Hz) Use either display list or (What will happen if refreshing is too slow or too storage tube technology fast?) Raster Scan Order Raster Scan Order What we do now: the electron gun will The electron gun will scan through the scan through the pixels from left to pixels from left to right, top to bottom right, top to bottom (scanline by (scanline by scanline) scanline) Horizontal retrace 3 Raster Scan Order Progressive vs. Interlace The electron gun will scan through the Progressive: Scan every scan line pixels from left to right, top to bottom Interlace: Scan only every other scan (scanline by scanline) line (e ven ->odd> odd ->e> ev en ->odd> odd …) - so the refresh rate becomes twice as fast Vertical retrace 0 Even scan 1 2 3 Odd scan 4 5 Standards Raster Scan Control NTSC: Interlaced, 525 line, 59.94Hz, Scan Controller (video adaptor) and frame 4:3 buffer DTV: Digit al ve rsion of NTSC , 480i , 4 :3 x Scan controller y HDTV: commonly 720p, 60Hz, 16:9 Blu-ray: 1080p Other standards? DAC Frame buffer 4 Frame Buffer Color is expensive … Frame buffer: the memory to hold the pixel intensity At least used to be values The more color you want, the more bits you Properties of a frame buffer that affect the graphics will need for each pixel performance: Exercise: 1024 x 1280 screen with Size: screen resolution Depth: color level 24 bits per pixel, how large is the frame 1 bit/pixel: black and white buffer? 8 bits/pixel: 256 levels of gray 1024 x 1280 x 24 / 8 = 4M Byte 24 bits/pixel: 16 million colors Speed: refresh speed @30fps = 120MB/sec Color Lookup Table A simple graphics system Say I am a poor man … I only have 3 bits per pixel Frame buffer can be part But I insist on having high quality pictures … Scan of the main memory Controller Use Color Look Up Table (LUT) R G B Frame 0 CPU Main Memory 1 buffer 2 You can still have 24 bits 3 in each of the color table 4 5 entries System bus 6 24 bit wide 7 3 bits/pixel frame buffer Problem? 5 Dedicated memory Graphics Accelerator Video memory: On-board frame buffer: Graphics Memory/ much faster to access Frame buffer Scan Frame A dedicated processor Graphics Scan Controller buffer for graphics processing Processor Controller CPU Main Memory CPU Main Memory System bus System bus CPUs vs. GPUs Graphics Accelerator 6 The Graphics Pipeline Graphics Bus Interface Graphics Bus Interface (2) PCI based technology PCI Bus becomes the bottleneck! Many devices are using it GaphicsMemoGraphics Memory / Other There is a lot of stuff needs to be Frame buffer Peripherals transmitted from main memory to graphics Graphics Scan memory (geometry, textures, etc) Processor Controller PCI Bus – 132 MB/s Example: 2M triangle, 90 Bytes each – 180MB > 132 MB (PCI bandwidth) System Bus – 800MB/s CPU Main Memory 7 Accelerated Graphics Port (AGP) AGP A dedicated bus that allows direct access of main memory AGP 1x is four times as fast compared to PCI! (now we have AGP 8x) Grappy/hics Memory/ Other Frame buffer Peripherals No more llblocal bus congestion! Graphics Scan More geometry can be processed! Processor Controller PCI Bus – 132 MB/s Direct execution of many graphics AGP 1x: 518 MB/s operations from main memory Fast!!! CPU Main Memory PCI Express Reading and Lab0 Bandwidth? Textbook Chapter 1, 2 AGP in fo: http: //deve loper. in te l.com /tec hno logy /agp Lab 0: Compile and run the sample OpenGL program posted on the class web site 8.