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 Moving along odd angles  (Read 1543 times) 0 Members and 1 Guest are viewing this topic.
69_Jeremy_69

Senior Newbie

Java games rock!

 « Posted 2005-01-07 20:53:10 »

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.
 1  2  3  4  5  6  7  8  9  10  11  12  13  14  15  16  17  18  19  20  21  22  23  24  25  26  27  28  29  30  31 `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?
69_Jeremy_69

Senior Newbie

Java games rock!

 « Reply #1 - Posted 2005-01-07 20:57:03 »

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?

woogley
 « Reply #2 - Posted 2005-01-07 21:32:04 »

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

first you need to find the angle between the two points. use this method:
 1  2  3 `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:
 1  2 `piece.x+=Math.cos(angle)*velocity;piece.y+=Math.sin(angle)*velocity;`

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

Senior Newbie

Java games rock!

 « Reply #3 - Posted 2005-01-07 21:47:59 »

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