Terminology
World Coordinate System (Object Space)
Representation of an object measured in some physical units.
Window
The rectangle definig the part of the world we wish to display.
Screen Coordinate System (Image Space)
The space within which the image is displayed.
Viewport
The rectangle on the raster graphics screen defining where the image
will appear. (Default is usually the entire screen.)
Viewing Transformation
The process of going from a window in a world coordinates to a viewport
in screen coordinates.
