Do not calculate path if destination is outside graph or inside an obstacle

General Grid graph
#1

I am using a GridGraph and using the AIPath + RVO.

If I set up ai.destination outside the graph the entity will try to reach the position with no errors.
I want to prevent if the ai tries to move outside the graph or into a collider (preconfigured collider2D),
because it has an OnReachDestination method, but it will never reach it.

Saw the recast graph navmeshcutting script, but just moved to 2D GridGraph to a high performance.
Tried IsPathPossible but it is allways returning true.

How could I prevent this?

AI path agent want to move into obstacle/other unit
#2

Hi

The easiest way to do this is to adjust the A* Inspector -> Settings -> Max Nearest Node Distance.
The path will fail if it cannot get within that distance to the goal.

Also note that OnReachedDestination is deprecated. I recommend that you use ai.reachedDestination or possibly ai.reachedEndOfPath instead.

1 Like
#3

Thank you, the Max Nearest Node Distance set to 0.1 works perfectly.

I remember now. I am not using ai.reachedEndOfpath because it was telling me allways that path was not reached because of the endReachedDistance was not 0 and whenCloseToDestination is set to Stop.

I am using a simple Corroutine to detect if was stoped near the reached distance instead the destination:

public IEnumerator OnReachDestination(){
    yield return new WaitUntil(() => Vector3.Distance(ai.position, ai.destination) < ai.endReachedDistance + 0.5);
    destinationReached = true;
}
#4

I missed something.

Given that square, where a is walkable and b is an obstacle.

a a a a  
a b b a  
a b b a 
a a a a

Now, with your help, the ai will “Path Failed” trying to reach b positions.
But the ai should calculate randomly to move inside the zone.

I was wondering that SearchPath was not void and it returns true or false depending if “Path Failed” or not.
So, what is the best mehod to have a response if SearchPath has fail?

#5

Hi

I’m not quite sure what you mean. Your message title says “Do not calculate path if destination is outside graph or inside an obstacle”. So I thought you didn’t want it to calculate a path close to those B positions?

#6

I do not want the ai tries to reach an outside graph or obstacle, so this is the reason because of I do not want the ai trying to reach an impossible destination. (Before changing “Max Nearest Distance Node” it tried to go outside the graph stopping near the wall).

But if with a random path calculation inside a square zone it tries to reach an impossible destination, I need to know if the path has failed (like the A*'s return log of “path failed” in the console) to control the errors.

–

Edit: I am thinking now that this will be not the best solition for that. But I am still wanting how to know to get a “path failed” response.

#7

Hi

If you want to see if it is reachable, then you can as you say originally use IsPathPossible.
The reason it always returned true when you tried to check if a path to outside the graph was valid was that it first finds the closest nodes to the start and end point. The closest node to a point outside the graph will be a point inside the graph, and there was probably a valid path to that node. However the Max Nearest Node Distance checks that you added later will also impact this check, so now it will work for you I think.

Another simpler solution perhaps could be to check the last path result using something like seeker.GetPath().error. That will be true if the last path failed.

1 Like
#8

Thank you, now I understand what means Max Nearest Node Distance, but it will be so usefull the GetPath().error.