Add SDK NavMeshGenerator to mefisto fork

mitm · September 4, 2017, 3:27am

I want to add a slightly modified version of the SDK NavMeshGenerator to the MeFisto94 AI fork of the jme3AI library.

The changes to it are very minor, Line 20 and 21 go away.

jMonkeyEngine/sdk/blob/b4a5071308db9c260ac556cba8e1d2297fe49ee2/jme3-navmesh-gen/src/com/jme3/gde/nmgen/NavMeshGenerator.java#L20


import com.jme3.scene.Mesh;
import com.jme3.scene.Node;
import com.jme3.scene.VertexBuffer.Type;
import com.jme3.scene.mesh.IndexBuffer;
import com.jme3.terrain.Terrain;
import java.io.IOException;
import java.nio.FloatBuffer;
import org.critterai.nmgen.IntermediateData;
import org.critterai.nmgen.NavmeshGenerator;
import org.critterai.nmgen.TriangleMesh;
import org.openide.DialogDisplayer;
import org.openide.NotifyDescriptor;
/**
 * Generates the navigation mesh using the org.critterai.nmgen.NavmeshGenerator class.
 * 
 */ 
public class NavMeshGenerator implements Savable {
    private org.critterai.nmgen.NavmeshGenerator nmgen;
    private float cellSize = 1f;

I add a LOG statement at line 28,

I change line 121 to log rather than displaying a dialog,

github.com

jMonkeyEngine/sdk/blob/b4a5071308db9c260ac556cba8e1d2297fe49ee2/jme3-navmesh-gen/src/com/jme3/gde/nmgen/NavMeshGenerator.java#L121


    mesh2.updateCounts();
    return mesh2;
}
private TriangleMesh buildNavMesh(float[] positions, int[] indices, IntermediateData intermediateData) {
    MeshBuildRunnable runnable = new MeshBuildRunnable(positions, indices, intermediateData);
    try {
        execute(runnable, timeout);
    } catch (TimeoutException ex) {
        DialogDisplayer.getDefault().notifyLater(new NotifyDescriptor.Message("NavMesh Generation timed out."));
    }
    return runnable.getTriMesh();
}
private static void execute(Thread task, long timeout) throws TimeoutException {
    task.start();
    try {
        task.join(timeout);
    } catch (InterruptedException e) {
    }

I uncomment line 133, and comment out line 134

github.com

jMonkeyEngine/sdk/blob/b4a5071308db9c260ac556cba8e1d2297fe49ee2/jme3-navmesh-gen/src/com/jme3/gde/nmgen/NavMeshGenerator.java#L133


        return runnable.getTriMesh();
    }
    private static void execute(Thread task, long timeout) throws TimeoutException {
        task.start();
        try {
            task.join(timeout);
        } catch (InterruptedException e) {
        }
        if (task.isAlive()) {
//            task.interrupt();
            task.stop();
            throw new TimeoutException();
        }
    }
    private static void execute(Runnable task, long timeout) throws TimeoutException {
        Thread t = new Thread(task, "Timeout guard");
        t.setDaemon(true);
        execute(t, timeout);
    }

This would then require CritterAI and jme3-terrain libraries to use this class.

This would then make MeFisto94 fork whole where you can generate and use the navmesh for pathfinding.

I wont do a pull unless approved here.

Darkchaos · September 4, 2017, 9:33am

Hey,
I am uncertain whether this would be a good addition, because usually you generate the NavMeshes before shipping the game and then have a thin library to do the path finding.

So maybe if we implement it, we could have different artifacts like jme3-ai-rt and jme3-ai or something. Which actually reminds me that the name itself is unsatisfying because it’s only navmeshing and not for instance the steering behaviors I have in MonkeyBrains…

What I did in my project is just using CritterAI directly and then generator = new org.critterai.nmgen.NavmeshGenerator(nG.cellSize, nG.cellHeight, nG.minTraversableHeight, nG.maxTraversableStep, nG.maxTraversableSlope, nG.clipLedges, nG.traversableAreaBorderSize, nG.smoothingThreshold, nG.useConservativeExpansion, nG.minUnconnectedRegionSize, nG.mergeRegionSize, nG.maxEdgeLength, nG.edgeMaxDeviation, nG.maxVertsPerPoly, nG.contourSampleDistance, nG.contourMaxDeviation);

So I am uncertain if we should add it to the AI library, but on the other hand a all-in-one library might also be handy, yeah.

mitm · September 4, 2017, 10:04am

I hadn’t thought about this,

I’ve been concentrating on wiki and NavMeshGenerator makes life real simple. I guess they can just copy it from the example repository once its up.

mitm · September 4, 2017, 10:24am

The steering behaviors included with the AI don’t really work as expected, actually they don’t work at all. Not one time did any vehicle avoid any obstacle. Every test I tried using different behaviors did exactly the same thing, i,e. just barged through the obstacles and followed the target after catching up to it.

Darkchaos · September 4, 2017, 11:33am

Well there is also a fork for that: GitHub - MeFisto94/MonkeyBrains: Agent framework for jMonkey Engine
Note though that it doesn’t only contain bugfixes but major reworks and design changes.

Basic behaviors should work, I actually posted screenshots of a simple multithreading test into the Screenshot Thread Sometime. The only thing I didn’t get to work properly was following a path, but at that time I was too exhausted to continue MonkeyBrains anyway.

A demo would be here MonkeyBrains/DemoSingleThread.java at myFork · MeFisto94/MonkeyBrains · GitHub

You can even make it work with the BetterCharacterControl then, however what I never figured out was combining NavMeshes and Steering Behaviors (Detour Crowd)