3-D Smooth Zooming

Ninad Jog and Bruce Lin

				ABSTRACT

This project aims at using novel data access methods and efficient screen-drawing algorithms to facilitate rapid and flicker-free zooming of a 2-dimensional starfield display. A starfield display uses dots to represent database items; the location and color of each dot being a function of the attributes of the item.

The project uses an existing FilmFinder application that embodies these
concepts. The X-axis shows the year of the film (ranges from 1920 to 1995)
and the Y-axis has the popularity (0-9). Each axis has a double-box slider 
that changes the scale of the axis to perform a zoom - for example, using the x-axis slider, you can zoom in to view films made between 1950 and 1995.
Zooming in causes the films' display rectangles to grow in size and also
move to different parts of the display.

The third dimension is the length of each film, which is varied using a range
slider. The display itself is still 2-dimensional, but the same principles that are used for the x and y ranges, apply.

For the zoom operation to appear continuous and smooth, three requirements have to be met.
	1) The underlying data structure should facilitate rapid indexing
	   to reach the required items without wasteful comparisons.
	2) The display should be updated frequently enough for the motion to
	   appear continuous.
	3) The erase and redraw operations should be fast to prevent flicker -
	   this can be done by buffering the image off-screen.

We have achieved smooth zooming by changing the data structures and data access methods (#1) as well as by increasing the update rates (#2).