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  Moving along odd angles  (Read 1267 times)
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Offline 69_Jeremy_69

Senior Newbie




Java games rock!


« Posted 2005-01-07 21:53:10 »

Ok currently I have a game piece object at position 1,1 and I move it to position 5,4.  Its just a simple repaint from there to here.

But in my move() call I want to animate the piece sliding on the board.  I already do simple move calls to float text or move a card in straight lines.  But its always only on one axis, either x or y.

And the moving of a game piece can be at any odd angle. So what type of equation should I be looking to use to figure out my where to redraw the gamepiece as it slides along the board.

I current brain storm was something like this.
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void setDestination(int destX, int destY) {
      this.destX = destX;
      this.destY = destY;
      
      if(currentX < destX){
            moveX = 1;
      }else{
            moveX = -1;
      }
      
      if(currentY < destY){
            moveY = 1;
      }else{
            moveY = -1;
      }
      
      moving = true;
}

void move() {      
      if(moving == false) return;
      
      if(currentX != destX)
            currentX += moveX;
      
      if(currentY != destY)
            currentY += moveY;
      
      if(currentX == destX && currentY == destY)
            moving = false;
}


Is there a better way to do this?
Offline 69_Jeremy_69

Senior Newbie




Java games rock!


« Reply #1 - Posted 2005-01-07 21:57:03 »

Actually thats pretty ugly.  It moves at an angle depending on the x and y.  Then it may move in a straight line to get to the bigger point.


\
\
 \
  \ _ _ _

So it works but is crap.  So whats the proper way to do this?

Offline woogley
« Reply #2 - Posted 2005-01-07 22:32:04 »

I'm pretty new to trig so I apologize if I'm totally wrong (I didn't test) Tongue

first you need to find the angle between the two points. use this method:
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protected double calcAngle(Point p1,Point p2) {
      return Math.atan2(p2.y-p1.y,p2.x-p1.x)*180.0/Math.PI;
}

note: it's a better idea to use atan2 because atan cannot handle a full circle...

Then to move along at that angle, use:
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piece.x+=Math.cos(angle)*velocity;
piece.y+=Math.sin(angle)*velocity;

where velocity is how fast you want it to move
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Offline 69_Jeremy_69

Senior Newbie




Java games rock!


« Reply #3 - Posted 2005-01-07 22:47:59 »

Looks good, I'll plug it in when I get home and try it out.
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