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Listing 24 . Source code for the program named VectorAdd04.

/*VectorAdd04.java Copyright 2008, R.G.BaldwinRevised 02/15/08 This program illustrates the addition of a Vector to aPoint producing a new Point. Both points and the vector are drawn on the screen.Tested using JDK 1.6 under WinXP. *********************************************************/import java.awt.*; import javax.swing.*;import java.awt.geom.*; class VectorAdd04{public static void main(String[] args){GUI guiObj = new GUI(); }//end main}//end controlling class VectorAdd04 //======================================================//class GUI extends JFrame{ //Specify the horizontal and vertical size of a JFrame// object. int hSize = 225;int vSize = 225; Image osi;//an off-screen imageint osiWidth;//off-screen image width int osiHeight;//off-screen image heightMyCanvas myCanvas;//a subclass of CanvasGUI(){//constructor //Set JFrame size, title, and close operation.setSize(hSize,vSize); setTitle("Copyright 2008,R.G.Baldwin");setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//Create a new drawing canvas and add it to the // center of the JFrame.myCanvas = new MyCanvas(); this.getContentPane().add(myCanvas);//This object must be visible before you can get an// off-screen image. It must also be visible before // you can compute the size of the canvas.setVisible(true); osiWidth = myCanvas.getWidth();osiHeight = myCanvas.getHeight(); //Create an off-screen image and get a graphics// context on it. osi = createImage(osiWidth,osiHeight);Graphics2D g2D = (Graphics2D)(osi.getGraphics());//Draw some graphical objects on the off-screen // image.drawOffScreen(g2D); //Cause the overridden paint method belonging to// myCanvas to be executed. myCanvas.repaint();}//end constructor //----------------------------------------------------////The purpose of this method is to add a Vector object// to a Point object and to draw the result onto an // off-screen image..void drawOffScreen(Graphics2D g2D){//Translate the origin on the off-screen // image and draw a pair of orthogonal axes on it.setCoordinateFrame(g2D); //Define one pointGM2D04.Point point = new GM2D04.Point( new GM2D04.ColMatrix(50,-25));//Define one vector.GM2D04.Vector vecA = new GM2D04.Vector( new GM2D04.ColMatrix(25,-50));//Add the Vector object to the Point object producing// a new Point object GM2D04.Point newPoint = point.addVectorToPoint(vecA);//Draw vecA in RED with its tail at the original// point. g2D.setColor(Color.RED);vecA.draw(g2D,point);//Draw the original point in GREEN. g2D.setColor(Color.GREEN);point.draw(g2D);//Draw the new point in BLUE. g2D.setColor(Color.BLUE);newPoint.draw(g2D); }//end drawOffScreen//----------------------------------------------------// //This method is used to set the origin of the// off-screen image and to draw orthogonal axes on the // off-screen image that intersect at the origin.private void setCoordinateFrame(Graphics2D g2D){ //Translate the origin to a point near the lower-left// corner of the off-screen image. g2D.translate(0.2*osiWidth,0.8*osiHeight);//Draw new X and Y-axes in default BLACK g2D.drawLine(-(int)(0.2*osiWidth),0,(int)(0.8*osiWidth),0);g2D.drawLine(0,-(int)(0.8*osiHeight), 0,(int)(0.2*osiHeight));}//end setCoordinateFrame method//====================================================////This is an inner class of the GUI class.class MyCanvas extends Canvas{ //Override the paint() method. This method will be// called when the JFrame and the Canvas appear on the // screen or when the repaint method is called on the// Canvas object. //The purpose of this method is to display the// off-screen image on the screen. public void paint(Graphics g){g.drawImage(osi,0,0,this); }//end overridden paint()}//end inner class MyCanvas}//end class GUI//======================================================//

Exercises

Exercise 1

Using Java and the game-math library named GM2D04 , or using a different programming environment of your choice, write a program that creates twelve random values in theapproximate range from -64 to +63. Use those values in pairs to define six mathematical vectors.

Draw the six vectors in a head-to-tail arrangement in alternating colors of green and blue with the tail ofthe first vector at the origin as shown in Figure 8 .

Compute and draw the sum of the six vectors in red with the tail of the sum vector at the origin.

Cause the origin of your reference frame to be at the center of your drawing and draw the axes for a Cartesiancoordinate system in the reference frame in black.

Cause the positive x direction to be to the right.

Cause the positive y direction be either up or down according to your choice.

Use a symbol of your choice to indicate the head of each vector.

Cause the program to display your name in some manner.

Figure 8 Screen output from Exercise 1.

Missing image.

Exercise 2

Using Java and the game-math library named GM2D04 , or using a different programming environment of your choice, write a program that creates four random values in theapproximate range from -128 to +127. Use those values in pairs to define two mathematical vectors.

Create a third vector as the sum of the first two vectors.

Using red, green, and blue, draw the three vectors in a way that illustrates the parallelogram rule for vectoraddition as shown in Figure 9 .

Cause the origin of your reference frame to be at the center of your drawing and draw the axes for a Cartesiancoordinate system in the reference frame in black.

Cause the positive x direction to be to the right. Cause the positive y direction be either up or downaccording to your choice.

Use a symbol of your choice to indicate the head of each vector.

Cause the program to display your name in some manner.

Because of the random nature of the vectors, you may need to run your program more than once to open up the vectordiagram and get a clear picture of the parallelogram rule for vector addition.

Figure 9 Screen output from Exercise 2.

Missing image.

-end-

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Source:  OpenStax, Game 2302 - mathematical applications for game development. OpenStax CNX. Jan 09, 2016 Download for free at https://legacy.cnx.org/content/col11450/1.33
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