Angle Question
I'm writing a program for a Pong-like game, but I'm having trouble with the angles. I'm using two variables: XSpeed and YSpeed, for the ball, and every timestep I add XSpeed to XPos and YSpeed to YPos, then I redraw the ball using the statement Draw.fillOval(XPos-Radius, YPos-Radius, Radius*2, Radius*2);--where Radius is the radius of the circle that is the ball, and Draw is an instance of the Graphics class. I have a method ChangeAngle() that randomly generates values for XSpeed and YSpeed. This is called whenever the ball bounces off of something, such as the top and bottom walls or a paddle. Anyway, the problem comes in when trying to make the ball move at approximately the same speed, regardless of what angle it's moving at. I attempted to solve this problem using square roots, such as Math.sqrt(MaxSpeed);, where MaxSpeed is XSpeed when YSpeed==0, or YSpeed when XSpeed==0. Unfortunately, this only works for 45-degree angles and straight lines. So... can someone either provide me with algorithms for other angles (I'd like to have as many potential angles as possible), or perhaps give me a better solution to the problem? Thanks. ^_^
EDIT: If it helps, here's the complete code of the program so far... it's not fully implemented, so a bunch of the instance variables don't do anything yet, and you'll probably find some random methods floating around.
import java.util.*;
import java.awt.*;
import java.applet.*;
import javax.swing.*;
publicclass Bounceextends Appletimplements Runnable
{
int
XPos,
YPos,
Pad1XPos,
Pad1YPos,
Pad2XPos,
Pad2YPos,
XSpeed=9,
YSpeed=9,
PaddleSpeed,
Radius=8,
PaddleHeight=50,
PaddleWidth=10,
MaxSpeed=4;
Image
ImageGen;
Graphics
DBG;
Random
Rand=new Random();
Color
BallColor=new Color(Rand.nextInt(256), Rand.nextInt(256), Rand.nextInt(256)),
Pad1Color=new Color(Rand.nextInt(256), Rand.nextInt(256), Rand.nextInt(256)),
Pad2Color=new Color(Rand.nextInt(256), Rand.nextInt(256), Rand.nextInt(256));
publicvoid start()
{
setBackground(new Color(Rand.nextInt(256), Rand.nextInt(256), Rand.nextInt(256)));
Thread Ball=new Thread(this);
Ball.start();
XPos=this.getWidth()/2;
YPos=this.getHeight()/2;
Pad1XPos=10;
Pad1YPos=this.getHeight()/2;
Pad2XPos=this.getWidth()-10;
Pad2YPos=this.getHeight()/2;
PaddleSpeed=MaxSpeed+1;
ChangeAngle();
}
publicvoid run()
{
Thread.currentThread().setPriority(Thread.MIN_PRIORITY);
while(true)
{
repaint();
try
{
Thread.sleep(10);
}
catch(InterruptedException ex)
{
}
Thread.currentThread().setPriority(Thread.MAX_PRIORITY);
if((XPos-Radius<=0&&XSpeed<0)||(XPos+Radius>=this.getWidth()&&XSpeed>0))
{
XSpeed*=-1;
ChangeAngle();
}
if((YPos-Radius<=0&&YSpeed<0)||(YPos+Radius>=this.getHeight()&&YSpeed>0))
{
YSpeed*=-1;
ChangeAngle();
}
XPos+=XSpeed;
YPos+=YSpeed;
}
}
publicvoid update(Graphics Draw)
{
if(ImageGen==null)
{
ImageGen=createImage(this.getSize().width, this.getSize().height);
DBG=ImageGen.getGraphics();
}
DBG.setColor(getBackground());
DBG.fillRect(0, 0, this.getSize().width, this.getSize().height);
DBG.setColor(getForeground());
paint(DBG);
Draw.drawImage(ImageGen, 0, 0,this);
}
publicvoid paint(Graphics Draw)
{
Draw.setColor(BallColor);
Draw.fillOval(XPos-Radius, YPos-Radius, Radius*2, Radius*2);
Draw.setColor(Pad1Color);
Draw.fillRect(Pad1XPos-(PaddleWidth/2), Pad1YPos-(PaddleHeight/2), PaddleWidth, PaddleHeight);
Draw.setColor(Pad2Color);
Draw.fillRect(Pad2XPos-(PaddleWidth/2), Pad2YPos-(PaddleHeight/2), PaddleWidth, PaddleHeight);
Draw.setColor(new Color(Rand.nextInt(256), Rand.nextInt(256), Rand.nextInt(256)));
Draw.drawString("XSpeed: "+XSpeed, 125, 225);
Draw.drawString("YSpeed: "+YSpeed, 375, 225);
}
publicboolean keyDown(Event e,int key)
{
returntrue;
}
publicvoid ChangeAngle()
{
int Num;
XSpeed/=Math.abs(XSpeed);
YSpeed/=Math.abs(YSpeed);
Num=Rand.nextInt(6);
switch(Num)
{
case 0: XSpeed*=Math.sqrt(MaxSpeed); YSpeed*=Math.sqrt(MaxSpeed);break;
case 1: XSpeed*=Math.sqrt(MaxSpeed); YSpeed*=-Math.sqrt(MaxSpeed);break;
case 2: XSpeed*=Math.sqrt(MaxSpeed); YSpeed*=Math.sqrt(MaxSpeed)/2;break;
case 3: XSpeed*=Math.sqrt(MaxSpeed); YSpeed*=-Math.sqrt(MaxSpeed)/2;break;
case 4: XSpeed*=Math.sqrt(MaxSpeed)/2; YSpeed*=Math.sqrt(MaxSpeed);break;
case 5: XSpeed*=Math.sqrt(MaxSpeed)/2; YSpeed*=-Math.sqrt(MaxSpeed);break;
}
}
}
