getting point on line at distance

[pepsicoder]

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)?

x1_________x3____x2
y1         y3    y2

Cheers for you help in advance

[newblack]

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

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 );

}

[pepsicoder]

cheers m8.

[lordofduct]

you missed a line of code there:

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 );

}

[newblack]

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

[pepsicoder]

Cheers to all.