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AEiE0804 Computer graphics

Computer-graphics fundamentals

  • Computer graphics studies generation, storage, manipulation, and display of visual information.
  • Interactive graphics combines user input with rendered output.
  • Graphics hardware covers display devices, controllers, processors, and input devices.
  • Graphics software provides modelling, transformation, viewing, rendering, and application interfaces.

Raster, vector, and display hardware

Display type Representation Strength Limitation
Raster-scan Picture as pixels on a grid Good for filled regions and images Aliasing and memory cost
Vector or random-scan Picture as line segments drawn directly Very sharp line drawings Poor for shaded scenes
  • Raster displays refresh the entire screen line by line.
  • Vector displays draw only the specified line paths.
  • Vector graphics represent images using mathematically defined primitives or paths such as points, lines, curves, and polygons; raster graphics store pixel samples.
  • Modern general-purpose monitors are raster based.
Technology Key idea Recognition cue
CRT Electron beam excites phosphor Older tube display
LCD Liquid crystal modulates backlight Thin flat panel
OLED Self-emissive pixels High contrast, no backlight

Raster-scan architecture essentials:

  • Frame buffer stores pixel intensity or color values.
  • Display controller reads the frame buffer and generates video signals.
  • Scan lines run left to right, top to bottom.
  • Horizontal retrace returns to the next line.
  • Vertical retrace returns to the top of the screen.

Graphics processors, devices, and software

  • A display processor offloads graphics tasks from the CPU.
  • A GPU accelerates transformation, clipping, shading, texturing, and rasterization.
  • Double buffering reduces flicker and tearing.
Device class Examples Common association
Output Monitor, plotter, printer, projector Present the image
Pointing input Mouse, trackball, joystick, touch panel Cursor control
Digitizing input Light pen, graphics tablet, scanner Direct graphics entry
  • Plotters are classic vector-style hard-copy devices.
  • Graphics libraries and standards improve portability and device independence.

Representative software and standards:

Item Role
GKS / ISO 7942 device-independent 2D graphics standard
PHIGS / ISO 9592 hierarchical retained-mode graphics standard
OpenGL cross-platform rendering specification and API

Recognition cues for computer graphics

  • "Line by line refresh" points to raster-scan display.
  • "Sharp engineering line drawing" often points to vector display or plotter.
  • "Pixel-addressable frame buffer" is raster architecture.
  • "Hardware support for rendering pipeline" indicates GPU or display processor.

Common traps in computer graphics

  • Raster and vector are representation/display methods, not image file formats only.
  • Resolution and aspect ratio are different quantities.
  • Input devices do not render output; they supply commands or coordinates.
  • A plotter is an output device, not a digitizer.

One-step examples for computer graphics

  • A 1920 x 1080 display has 2,073,600 addressable pixels.
  • A monochrome frame buffer for 1024 x 1024 with 1 bit per pixel needs \(1024^2/8 = 131072\) bytes.
  • A color-depth increase raises frame-buffer memory even if screen size stays the same.

Computer-graphics revision box

Raster means pixel grid; vector means drawn line segments. Frame buffer and scan controller are central in raster systems. Display processors and GPUs accelerate graphics. Keep device categories straight: monitor/plotter are output, mouse/tablet are input.