Forums » Help » Detecting an object between two objects

Hey, new guy here... I know I can get the length and angle that one entity is from another, but is it possible to tell if there is an entity directly between the two?

Thanks,
TraDekan

Pretend for a moment that you draw a line between EntityA and EntityB.
Your question, I think, is how to tell if a third entity is touching that line.

Perhaps useful?

If C is in the middle of A and B then angle(A,C) + angle(B,C) = Pi.
So you have to evaluate if

( Angle(A,C) + angle(B,C) - Pi ) % (2*Pi) ) < threshold.

Another way of solving this :
compute the distance from C to AB.
During this process, you will know if the normal projection of C on AB is within AB or not : this is the first thing you want to check.
Then you check that the distance from C to AB is not too big.
So based on this post :
http://stackoverflow.com/a/6853926/856501

// returns wether (x,y) point is within ( (x1,y1); (x2,y2) ) segment
// and nearer than maxDistance.
function isWithin(x, y, x1, y1, x2, y2, maxDistance) {

  var A = x - x1;
  var B = y - y1;
  var C = x2 - x1;
  var D = y2 - y1;

  var dot = A * C + B * D;
  var len_sq = C * C + D * D;
  var param = dot / len_sq;

  if ( (param < 0) || (param >1) ) return false; 

  var xx, yy;

   xx = x1 + param * C;
   yy = y1 + param * D;

   return (sq(x-xx)+ sq(y-yy)) < sq(maxDistance);
}

function sq(x) {return x*x }

Thanks!! Those help a lot.