Alternate shorter path, but not too close to the target?

Beginner Questions
#1

When I moved my game to newer version of unity, I found that new internal pathfinding works bad in some areas of game level (agent.hasPath && agent.path.corners.length == 0).
I bought Astar, but here now is a little difference, how it works.
Earlier, AIs always move to the edge of a bridge or a river barrier, to follow the enemy and shoot it.
Now, they live this place to find a way to the river, to get closer to enemy as possible. (about 1km path)
Is here any existing setting or method to use old way? I currently only found GetNearest(position) to find nearest node.
How to find nearest point to the target on the nearest nodes (cyan point on the pic)?
I hope pics below will help to convey the idea.

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#2

Hi

Are you sure the river was actually connected to the navmesh that the agents stood on (the bridge) when using Unity’s system? I have a hard time seeing that Unity’s system would not find a path that took the agent as close as possible to the target.

#3

Yes, the river and the bridge are the same navmesh. I made simplified geometry of the level (only walkable areas) to use for navmesh calculation. I use it also for recast graph. It looks the same in all cases.
I have tested it many times and did some screenshots.
It always works as I wrote above, in unity 4.7.2.
Yellow vertical 2m lines are unity’s pathfinding path corners.
Friendly AI uses snake’s root transform as destination and finds a path to nearest navmesh edge, closest to snake.
In unity 2017, friendly AI not able to find a path to the snake at all (too long path?).
My question only - is any chance to find this nearest edge to simulate old behavior in unity 2017 with Astar?

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#4

Hi

Ah, I see. So Unity had some kind of length restriction.
Well, this is easy enough to emulate, though it requires accessing an internal part of the code to get the distance information:

You create an ITraversalProvider (for more info, see the bottom of this page: https://arongranberg.com/astar/docs/turnbased.html#ITraversalProvider) which prevents the paths from being too long. The G score is the cost to move from the start of the path to that node.

public class MyCustomTraversalProvider : ITraversalProvider {
    public float maxDistance = 100f;
    public bool CanTraverse (Path path, GraphNode node) {
        if ((IPathInternals)path).PathHandler.GetPathNode(node).G > Int3.FloatPrecision * maxDistance) {
            return false;
        }
        return DefaultITraversalProvider.CanTraverse(path, node);
    }

    public uint GetTraversalCost (Path path, GraphNode node) {
        return DefaultITraversalProvider.GetTraversalCost(path, node);
    }
}

Then when you search for a path you will need to assign the traversal provider.

var path = ...;
path.traversalProvider = new MyCustomTraversalProvider();
path.calculatePartial = true;
seeker.StartPath(path, ...);

If you are using one of the built-in movement scripts you can either subclass it and override the SearchPath method, or you can set ai.canSearch to false and do all path searches using a separate script.

#5

Thank you! I’ll try to implement this

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