1.11 Game 2302-0130: putting the game-math library to work  (Page 2/20)

Preview

In this module, I will present and explain four programs that use the game-math library named GM2D04 . The purpose of the first program named VectorAdd05 is to use the addVectorToPoint method of the GM2D04.Point class to translate a geometric object from one location in space to a different location in space.

The purpose of the program named VectorAdd05a is to accomplish the same translation operation, but in a possibly more efficientmanner.

The purpose of the program named VectorAdd06 is to teach you how to do rudimentary animation using the game-math library.

The purpose of the program named StringArt01 is to teach you how to use methods of the game-math library to produce relatively complexdrawings.

All of the programs are interactive in that they provide a GUI that allows the user to modify certain aspects of the behavior of the program.

I will also provide an exercise for you to complete on your own at the end of the module. The exercise will concentrate on the material that you have learnedin this module and previous modules.

Discussion and sample code

The game-math library named GM2D04

The game-math library that we are developing in this collection of modules has undergone several updates since its inception in the first module. The versionof the library that existed at the end of the previous module was named GM2D04 . No revisions have been made to the library since that module and we won't be makingany revisions during this module.

The source code for the library named GM2D04 is provided for your convenience in Listing 17 near the end of the module. Documentation for the library was provided in the earlier module titled GAME 2302-0125: Vector Addition .

The program named VectorAdd05

The main purpose of this program is to use the addVectorToPoint method of the GM2D04.Point class in the game-math library to translate a geometric object from one location in space to a different location in space.This is illustrated in Figure 1 , which shows one hexagon (shown in black) having been translated by 50 units in both the x and y directions and coloredred at the new location.

Figure 1 Translation of black hexagon to location of red hexagon.

Various other game-math library methods are also used

Along the way, the program uses various other methods of the classes in the game-math library named GM2D04 to accomplish its purpose.

The program initially constructs and draws a black hexagon centered on the origin as shown in Figure 1 . The six points that define the vertices of the hexagon lie on a circle with a radius of 50 units. The points at the verticesand the lines that connect the points are drawn. In addition, the program causes the hexagon to be translated by 50 units in the positive X direction and 50units in the positive Y direction. The translated hexagon is drawn in red. The original black hexagon is not erased when the translated version is drawn in red.

A graphical user interface (GUI)

A GUI is provided that allows the user to specify the following items and click a Replot button to cause the drawing to change: