getting point on line at distance

Does some one know of a fast method of finding point x3,y3 when we know points x1,y1 x2,y2 and distance (heading from x1,y1 towards x2,y2)?

Code:

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x1_________x3____x2
y1        y3    y2

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Cheers for you help in advance :)

you need to define a vector pointing from (x1,y1) to (x2,y2), normalize it and scale it by the distance:

Code:

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function getPointAtInterval( p1:Point, p2:Point, t:Number ) : Point
{
 
  var x3:Number = p2.x - p1.x;
  var y3:Number = p2.y - p1.y;
 
  var length:Number = Math.sqrt( x3 * x3 + y3 * y3 );
 
  x3 /= length;
  y3 /= length;

  x3 *= t;
  y3 *= t;

  return new Point( p1.x + x3, p1.y + y3 );

}

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cheers m8.

you missed a line of code there:

Code:

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function getPointAtDistance( p1:Point, p2:Point, dis:Number ) : Point
{
  //get vector 
  var x3:Number = p2.x - p1.x;
  var y3:Number = p2.y - p1.y;
 
  //normalize vector
  var length:Number = Math.sqrt( x3 * x3 + y3 * y3 );
  x3 /= length;
  y3 /= length;

  //scale vector
  x3 *= dis;
  y3 *= dis;

  //add vector back onto initial point and return
  return new Point( p1.x + x3, p1.y + y3 );

}

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oops, thanks, lordofduct! i'll edit the original post.

Cheers to all.