Multiple Areas - NPC cant find nodes

Beginner Questions
#1

Hi everyone.

I’ve created a Level that contains several “Patches” (so called “Areas” i think) of meshes that are combined into one big navmesh.

Now, my AI does have a “Chase” behaviour. basically, when it sees the player, it chases the player. Now, it seems as if when the AI tries to generate a path towards a player that passed over multiple of those “Areas”, the Pathfinding drops this Error: “Couldn’t find a close node to the end point”.

That makes totally sense to me - i guess that the seeker tries to generate a path from one Area to another (which of course is not possible), and therefore generates this error. I’ve read in other threads that a possible solution to make an NPC stick to his area (and only use all avaiable nodes on the area he is on) is to use NNConstraints, yet i failed to implement them.

Could anybody shine some light on this mysterious NNConstraints and how to use them properly? :slight_smile:
Or maybe name a different approach to solve my problem and make an NPC stick and only generate paths in one area?

Thanks a lot upfront!

Cheers

EDIT:

Here is a Code snippet of my current path-generation for the chase behaviour (at the moment not using the generated nnInfo.pos as target, because it dropped null ref. errors):

    GraphNode node = AstarPath.active.GetNearest(transform.position, NNConstraint.Default).node;
    uint areaID = node.Area;
    //Then you want to configure the NNConstraint to only return nodes which can be reached from the start node:
    NNConstraint nn = new NNConstraint();
    nn.constrainArea = true;
    nn.area = (int)areaID;

    NNInfo info = AstarPath.active.GetNearest((target.GetValue() as Transform).position, nn);
    
    m_generatePath = false;
    pathSeeker.StartPath(transform.position, (target.GetValue() as Transform).position, OnPathComplete);


    m_currentRepathCounter = 0;
#2

Hi

I suspect that the GetNearest search is being limited by the maximum search distance.
Try increasing the A* Inspector -> Settings -> Max Nearest Node Distance value.

#3

Hi aron,

Thanks for the reply. The Problem is, with the code that i posted above, the “NNinfo info” always returns null. When i then try to create a path using the gathered info via “pathSeeker.StartPath(transform.position, info.clampedPosition, OnPathComplete);” the seeker tries to create a path to the scene-origin (0,0,0).

As if he couldnt find the specified node. Perhaps there is a problem in the Area-ID conversion from uint to int? (as the Graphnode node only returns a uInt, but the NNConstraint only accepts an int)

Cheers and thanks upfront!

#4

Hi

When searching for a nearest node, it will not go on and search forever, it will stop unless it finds a node within the Max Nearest Node Distance value.

Note that when just using a regular path search, it will do pretty much the same thing as you do, that is: search for the closest node to the target that it can actually reach (i.e is in the same area).

#5

ahh okay… with that info now the error is also easy to reproduce… :slight_smile:
in my current case the error occurs not on areas that overlap, but when the chased-object gets out of the “maxNearest” distance.
so basically, when i get the error that the NPC cant find the path, it makes no sense repeating the search in the “OnPathComplete” callback, since nothing will change, right?

so i guess my options are: increase “maxNearest” even further (performance hit?), or abort the path-search?

thanks for the quick reply!

#6

actually i just figured out a third option… generate a new point that is in the maxNearest range, between the NPC and the target… gonna try this one, i guess?