Interactive Input Techniques • Basic positioning methods • Constraints • Grids • Gravity fields • Rubber-band methods • Sketching • Dragging
Positioning techniques • There are various techniques used for positioning. • Positioning means location, which is one of the basic graphical input techniques. • For geometrical modelling, positioning is very important, as the user frequently designs a new element of the model or repositioning an existing one. • While working on the screen the position is used to insert a symbol or to indicate the end point of a line or three points on a curve.
Continue… • For positioning the desired spot on the screen , the cursor or tracking cross is moved to that location and then the information is passed to the computer memory by pressing a button or key. • There are positioning constraints which can be overcome by using symbols guidelines, feedback and the use of rubber band techniques.
Basic positioning techniques • Used to specify a location for an object or a character string • The cursor is moved to the desired location. • A button is pressed to fix the object at this location.
Continue… • Used to draw lines
Continue… • Used to place the cursor at a predetermined position
Constraints • Used to achieve predetermined orientations and alignments • Common constraints • Horizontal alignment
Continue… • Vertical alignment
Grids • Used to round coordinates positions to the nearest grid intersection
Continue… • Useful for positioning and aligning objects and text • Grids can be displayed or invisible
Gravity field • Used to connect a new line to a previously drawn line • Normally the gravity field is not displayed
Rubber band Methods • Used to construct and position straight lines
Continue… • Used to construct circular arcs
Continue… • Used to scale objects
Continue… • Used to distort objects by allowing only the line segments attached to a single vertex to change
Sketching • Uses rubber-band methods to create objects consisting of connected line segments
Continue… • Uses stroke techniques to create curved figures
Continue… • A variety of brushes can be provided • Different thicknesses • Different textures • Different colors (including background) • Even patterns
Dragging • Used to reposition objects • Select an object from the menu • Position the object • Release the objects