CSci 480 Lecture Notes

Week Four, (Fall) Wednesday, (Summer) Tuesday: Graphics Hardware

(Fall) Homework Assignment

The two-point form for the equation of a line: 
  (y - y1) / (x - x1) = (y2 - y1) / (x2 - x1)
To rotate a point about the origin (from p1 to p2): 
  x2 = x1 * cos(theta) - y1 * sin(theta)
  y2 = x1 * sin(theta) + y1 * cos(theta)
Figure 4.1 shows various components in a networked graphics system. The key element is the graphics workstation.

4.1 Hardcopy Technologies

Image quality depends on dot size and adressability (dpi).

Figure 4.2 shows the effects of various ratios of dot size to interdot distance (1 / adressability).

Resolution is related to dot size and can be no greater than adressability: number of distinguishable lines per inch.

Dot-matrix printer. Pen plotter (drum and flatbed). Laser printer (see figure 4.4). Ink-jet printer. Thermal-transfer printer. Thermal sublimation dye transfer printer. Film recorder (camera with a CRT).

4.2 Display Technologies

Interactive computer graphics demands display devices whose images can be changed quickly. The CRT is the most common display device.

Refresh rate: 70+ per second is sufficient. 60 per second will flicker.

Terms: flourescence and phosphresence. Persistence is the time it takes for the phosphresence to decay 10 percent. Critical fusion frequency (CFF) varies with persistence.

Color TV and color raster displays use a shadow-mask CRT (see figure 4.6).

Liquid crystal display (LCD) is popular for laptop computers (see figure 4.7). An active matrix LCD panel has a transister at each grid point. This allows proportional changes in liquid crystal state and for the state to change quickly. It also allows the cell to be brighter because it can stay on all the time without being refreshed.

LCDs are also used in head-mounted displays for VR applications.

Other displays include the electroluminescent display, the projection CRT, and a light-valve projection system.

4.3 Raster-Scan Display Systems

Most raster displays have some specialized hardware (graphics controller or display coprocessor) to assist in scan converting primitives and for pixel block operations. Some of the newer graphics controllers have specialized 3D chips for the fast display of polygons based on standard graphics libraries such as OpenGL or ActiveX.

4.3.1 Simple Raster Display System

See figure 4.8. The video controller often includes a video look-up table (LUT) which is filled by the current application. For example, Microsoft Windows supports 8-bit display (256 colors) selected from a pallet of millions of colors. The current application fills the LUT with its own values for each of the 256 colors. This results in color corruption of other windows that do not have the current focus.

Advantages Disadvantages
Inexpensive Scan conversion in software is slow
  CPU contention with video controller for RAM

4.3.2 Raster Display System with Peripheral Display Processor

See figure 4.11.

Advantages Disadvantages
Better performance More costly

4.3.4 Raster Display System with Integrated Display Processor

See figure 4.12. This is a single-address-space (SAS) display system architecture. The CPU and Display processor have to contend for access to system memory. This is compensated for by the simplicty of homogeneous memory access.

Advantages Disadvantages
Simplicity Memory contention
  Virtual memory overhead
  Kernel space (OS call)
vs application space
Input Devices for Operator Interaction

Locator Devices

Keyboard Devices

Valuator Devices

Choice Devices

4.5 Input Devices for Operator Interaction

This page established September 23, 1998; last updated September 22, 1999.