1. Computer Graphics - a beginning.   

The main areas where computer graphics is used are 



       Business Graphics  
       Scientific Graphics or Visualisation  
       Solid Modelling  
       VLSI design  
       Animation  
       CAD/CAM  
       Image Processing  
       Architectural design  
       Pretty Pictures
Surprise!!

We will look at a graphics system that will give us enough flexibility to cater for most of the above requirements.

1.10. Drawing Areas.   

Computer Graphics uses the X-Y coordinate system = Cartesian. Any point P = (x,y). Normally only 1 quadrant is used ie (+x,+y) but where does screen sit? 


     
Cartesian Coordinate System

    
             Fig. 1.13 : Cartesian Coordinate System
For example a Gigi Graphics terminal (normally) sits in lower quadrant yet always has +ve coordinates. Similarly for an X workstation.
There are a number of things we must consider when using/designing a graphics system: 
 1) What orientation is the screen?

 2) What are maximum coordinates available?

    ie physical maximum in inches-mm etc

    or logical maximum in coordinate points.

 3) What happens if (x,y) > (maxx,maxy)?

    Physically or logically?

We must know the answers to these questions if we are to be intimate with the devices ie write routines to drive the device. We will initially look at output and input devices and then at the X Window System and later look at writing our own device drivers for a simple graphics package. Surprise!!