Flash MX 2004 Games : Art to ActionScript

Flash MX 2004 Games
Figure B.6 Using Excel to chart exponential curves
The tweening example project
In addition to the Excel spreadsheets of the curves, there is the Flash project ‘Examples\
AppendixB\tweening.fla’ to help you to understand how this stuff works and what the results
look like.
The tweening project consists of a screen that contains two check boxes to select easing in and
easing out, and four radio buttons to choose the curve type. If you deselect both the ease-in and
-out options then you will get a linear interpolation. The aim of the application is to allow you to
click anywhere in the white area and then the yellow dot will move from its current location to
the new location in one second, leaving behind a trail that gives an indication of how the speed
of the motion accelerates and decelerates over time. Try running the application now and you
will get a feel for the different curves involved. The code inside the project uses the code snippets
already outlined and introduces a point class. As you know from Chapter 10, keeping data and the
manipulation of data together is a very useful technique; it makes your code more robust and easier
to modify and is highly recommended. To create a new point, simply use the ‘new’ keyword.
The function ‘point’ assigns values to the data and sets up pointers to function calls. Then to set
a point you can use the method ‘set’ and to add and subtract you can use the methods ‘add’ and
‘sub’. The results of the code snippet here would be to set ‘offset’ to the point (2, −18).
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