CS488 - Introduction to Computer Graphics - Lecture 3

Comments and Questions

Output Devices

Main device from the beginning was the colour cathode ray tube (CRT)

CRT

Types of CRT

Colour raster -- operational principles
- Three colour primaries ==> three frame buffers
- Shadowmask technology

Benefits of CRT

Very inexpensive
Good resolution
Easy colour calibration
High contrast
Good field of view
Comet-free motion
Adjustable focus

Drawbacks of CRT

Heavy and big
Power hungry
High voltage
Dim

LCD

Key components

Back light
Programmable filters -- one per colour primary per pixel
- Each filter a cell of analogue (!!) DRAM
- with liquid crystal (LC) between the plates of the capacitor
- LC rotates polarization depending on the electric field
- polarization-selective filters do the rest

Advantages

small
light
not as power hungry as CRT

Disadvantages - most of these are back light problems

directional view
back light consumes power
not very bright
poor extinction
hard to calibrate colour

Input Devices

Two types of device

Text input devices
Pointing devices

Device input modes

Request
- Normally used for text input
Sample
- Fast, because OS-free
- Everythinbg bad, because OS-free
- OS-mediated sampling
Event
- Good programming abstractions

Modes can operate differently at hardware and software levels.

Event-based programming

Event loop
- blocking
- non-blocking
Callbacks
- abstrtacted into toolkits
- check example in 4.6.

Events can be as simple or elaborate as you like

Abstraction boundaries rarely respected.

Geometry

Euclid and the Greeks

Of course, it's completely unfair to give the Greeks all the credit.

Descartes

Points are pairs (triples, etc)

Connects geometry to algebra.
Computers do algebra, not geometry.

Points morphed into vectors.

By trying to define addition so that algebra works.
Makes geometry challenging as an interpretation of algebra!