• This feature is of the greatest importance to a user
• Some onscreen input selection features are,
- Boxes - a good example of this method is the zoom boxes
- Types - all objects of a certain type are selected
- Names - in some systems parts are named, and these can be used for reference.
- Markers - symbolic markers can be placed on the screen to allow easy differentiation between object (like in Ideas)
- Layers - drawings can be layered up, which allows easy separation of distinctive parts. One example is a factory layout, including separate layers for machines, plumbing, electrical, HVAC, etc.
• Objects often require manipulation on the screen, and certain parameters defined by a number of techniques,
- select two points (they define a translation vector)
- select a line (a direction vector)
- about a pivot point by 1 angle (2 angles for 3D)
- a magnification about a point by a factor
- a copy with an offset for each copy
- a copy with a rotation for each copy
• The CRT is taken for granted now, but previously CAD systems underwent many metamorphosis.
• The array of current and previous hardware input devices are,
• Future hardware input devices include,
- scanned input and recognition
• Previous output devices include,