# Recalculate path on runtime

I’m making a tower defense game. My game has a mechanism to spawn and drag towers during runtime. I use linerenderer to draw the path from start point to end point (I use ABPath.Construct). I want to know how to recalculate the path and redraw the linerender every time I drag the tower.

Do you want to recalculate the path during the drag? Or only when dropped?

If you want to do it on drop, I recommend using a collider and running it off of a collision mask layer. Then you can recalculate the collision area when you drop the item, and paths will update at the point. The nice thing about a collision area is that it will not be very taxing on the system since you can update just the zone around the tower, without needing to recalculate the ENTIRE map.

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Thanks for your response, everything seems fine now. Can I ask one more question: how to check whether the path from point A to point B is blocked or not?

This is what I am using for figuring out which food objects can be gotten to by my goblins. This.transform is the goblin. It establishes node1 (start), and node 2 (the nearest vector3 transform position of a food object by pathable distance). It then checks if the path is even possible using the answer to your question: pathutilities.ispathpossible(node1, node2).
It then loops through all of the foods I have and figures out which is the closest.

``````for (int i = 0; i < _foodTransforms.Count; i++)
{
GraphNode node1 = AstarPath.active.GetNearest(this.transform.position, NNConstraint.Walkable).node;
Vector3 _temptransform = new Vector3(_foodTransforms[i].transform.position.x + 0.5f, _foodTransforms[i].transform.position.y + 0.5f, _foodTransforms[i].transform.position.z);
GraphNode node2 = AstarPath.active.GetNearest(_temptransform, NNConstraint.Walkable).node;
if (PathUtilities.IsPathPossible(node1, node2))
{
_distance = Vector3.Distance(this.transform.position, _temptransform);
//_distance = Vector3.Distance(this.transform.position, _foodTransforms[i].transform.position);
if (_distance < _nearestDistance)
{
_target = _foodTransforms[i];
_targetName = _foodTransforms[i].name;
_nearestDistance = _distance;
Vector2 _direction = (_target.transform.position - transform.position);
if (_target.position.x > transform.position.x) _facingRight = true; else _facingRight = false;
if (_facingRight) transform.localScale = new Vector3(-1f, 1f, 1f); else transform.localScale = new Vector3(1f, 1f, 1f);
}
}
}
``````