1/14/04

A general graphics system includes:

  1. Processor
  2. Memory
  3. Frame buffer
  4. Output devices
  5. Input devices

Most of you in this class probably have fairly sophisticated graphics systems. Modern video cards seldom have less than 2 mb of memory and typically have 8 mb or more. We talked about the frame buffer in some detail. Early display systems were very frugal in the use of frame buffers, resulting in less resolution, fewer colors, and a lot of extra work (e.g. for hidden surface algorithms). Modern systems have memory to burn, so the frame buffer is not likely to be a limiting factor in producing images. The display devices present more of a limitation. (You may have run across .25 mm dot pitch monitors, but have have you seen .10 mm ones?)

We discussed the mechanics and arithmetic of raster displays. How many bytes are required for a given resolution and number of colors? We compared vector and raster displays, and talked about interlaced vs. noninterlaced raster imaging.

The mouse is a ubiquitous input device. What are some others? What are their advantages and disadvantages?

Viewing objects

We tend to identify objects and our perception of them, but these are two completely different notions.

A camera offers one means of projecting an object into an image. An x-ray machine gives another. How are these different?

We discussed the "pinhole camera" and "synthetic camera" (Chapter 1 of our text) which offer two similar ways of projecting three dimensions into two. The pinhole camera puts the projection plane behind the viewpoint, so the projected image is upside-down. The synthetic camera puts the projection plane between the scene and the viewpoint. When objects are relatively close to the viewpoint, foreshortening occurs: edges closer to the viewer appear longer. When objects are relatively far away this effect is reduced. If the view point is "infinitely far away" from the objects (i.e., we use a parallel projection), distances of parallel edges are preserved. Shadows cast by the sun can be thought of as parallel projections.

Please read Chapter 1.