Navmesh generation with weights

jay · May 26, 2019, 7:41pm

Dear everybody,
I am writing my thesis project and am to extend software based on JME3.
I have a scene and can generate a Navmesh for that scene.
What I would like to do is weigh that Navmesh.
That in itself shouldn’t be a problem.
What is a problem though is finding the code where the navmesh generation is implemented.
I am certain it happens inside critterai, but I cannot find the code for it to save my life.
I can find a java implementation ( GitHub - bkmeneguello/cai-nmgen ),
I can find the code in jme3ai that uses critterai (doc-examples/NavMeshGenerator.java at master · jMonkeyEngine/doc-examples · GitHub), but I can’t find the thing itself.

Can someone point me into the right direction, please?

Best

jayfella · May 26, 2019, 7:48pm

This?

github.com

bkmeneguello/cai-nmgen/blob/master/src/main/java/org/critterai/nmgen/NavmeshGenerator.java

/*
 * Copyright (c) 2010 Stephen A. Pratt
 * 
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 * 
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 * 
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.

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jay · May 26, 2019, 7:54pm

Hi and thanks for your answer!

Yeah, I’ve posted the link to this repo in my post.
The thing is that I am not sure if that’s the actual implementation used in critterAI and therefore, JME3ai.
Then again, “package org.critterai.nmgen”… Well… I guess that’s the one used in JME3ai?
Can anyone confirm this is the implementation used?
Thanks!

mitm · May 26, 2019, 11:57pm

As far as I know this is the source from the things I gathered from the forums.

https://wiki.jmonkeyengine.org/jme3/advanced/jme3_ai.html

oxplay2 · May 27, 2019, 9:13am

thanks to @mitm im using Recast4J GitHub - ppiastucki/recast4j: Java Port of Recast & Detour navigation mesh toolset

that is great and allow navmesh tile building. very good lib.

im not sure what you mean by weights, but you could search if there is something like this.

but for easy game usage JME version might be faster/easier to use. links post above.

yn97 · May 27, 2019, 8:03pm

Would you help me with this?
I need to pass a vector3f point and if it is not traversable then returns the nearest position to that point…

oxplay2 · May 27, 2019, 9:48pm

you mean me? im not using JME ai. but looking at topic

- Get the nearest cell to the supplied position
- and place the returned position in that cell.

this mean you just provide location and it auto search nearest cell and if its in cell, then position inside cell, if not, then closest location to nearby cell.

so i think it should work like you need, it dont?

yn97 · May 28, 2019, 1:02am

maybe, I will test it…
and does it compute a path to the given point to check is it traversable?

oxplay2 · May 28, 2019, 7:36am

no, like in recast, nearest point mean nearest point, you can calculate straight line from A to B only.

pathfinding can find path only on traversable navmesh.

if point you provide into method is on navmesh i assume this method is only to get position on it, not to calculate path, you probably need find other method.

i can only look at https://wiki.jmonkeyengine.org/jme3/advanced/jme3_ai.html
and at files of jme AI. i only see mthods like computePath, onMove, getPath, goToNextWaypoint methods that you need to calculate pathfinding.

mitm · May 28, 2019, 4:49pm

Have you tried using warp?

github.com

MeFisto94/jme3-artificial-intelligence/blob/928fa1cdd6d3afac2364e4d250ea989b2ccf84ff/AI/src/com/jme3/ai/navmesh/NavMeshPathfinder.java#L77


      
              return currentPos3d;
          }
          
          /**
           * Get the nearest cell to the supplied position
           * and place the returned position in that cell.
           * 
           * @param position to place in the nearest cell
           * @return the position in the cell
           */
          public Vector3f warpInside(Vector3f position) {
              Vector3f newPos2d = new Vector3f(position.x, position.y, position.z);
              Cell cell = navMesh.findClosestCell(newPos2d);
              position.set(navMesh.snapPointToCell(cell, newPos2d));
              return position;
          }
          
          /**
           * Test if the position is inside a cell of the nav mesh.
           * @return false if it falls outside a cell, not in the navmesh.
           */

github.com

MeFisto94/jme3-artificial-intelligence/blob/928fa1cdd6d3afac2364e4d250ea989b2ccf84ff/AI/src/com/jme3/ai/navmesh/NavMeshPathfinder.java#L61


      
              this.entityRadius = entityRadius;
          }
          
          /**
           * Warp into the scene on the nav mesh, finding the nearest cell.
           * The currentCell and position3d are updated and this new
           * position is returned. This updates the state of the path finder!
           * 
           * @return the new position in the nearest cell
           */
          public Vector3f warp(Vector3f newPos) {
              Vector3f newPos2d = new Vector3f(newPos.x, newPos.y, newPos.z);
              currentCell = navMesh.findClosestCell(newPos2d);
              currentPos3d.set(navMesh.snapPointToCell(currentCell, newPos2d));
              currentPos3d.setY(newPos.getY());
              currentPos.set(currentPos3d.getX(), currentPos3d.getZ());
              return currentPos3d;
          }
          
          /**
           * Get the nearest cell to the supplied position

Otherwise try one of the methods here.

github.com

MeFisto94/jme3-artificial-intelligence/blob/928fa1cdd6d3afac2364e4d250ea989b2ccf84ff/AI/src/com/jme3/ai/navmesh/NavMesh.java

package com.jme3.ai.navmesh;

import java.io.IOException;
import java.util.ArrayList;

import com.jme3.ai.navmesh.Cell.ClassifyResult;
import com.jme3.export.InputCapsule;
import com.jme3.export.JmeExporter;
import com.jme3.export.JmeImporter;
import com.jme3.export.OutputCapsule;
import com.jme3.export.Savable;
import com.jme3.math.Vector2f;
import com.jme3.math.Vector3f;
import com.jme3.scene.Mesh;
import com.jme3.scene.VertexBuffer.Type;
import com.jme3.scene.mesh.IndexBuffer;
import com.jme3.util.BufferUtils;
import java.nio.FloatBuffer;

/**

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In recast, you set Area Types and Ability Flags and then use path filters. Much better approach. Significantly harder learning curve though.

mitm · May 28, 2019, 10:17pm

When using jme3AI I would think since its such a narrow use library maybe when you build the navmesh you should only pass in traversable geometry.

Mark your geometry with materials or some other method that will allow you to grab only those traversable geometry.

Use the slope, height, radius other settings to refine those areas.

With recast, you have Area Types and Ability flags where you set an area by type like ground, water, road, etc and then you use ability flags on those polygons like walk, swim, jump, disabled etc and then use a filter tailored to the character which says if they can walk, swim, or jump so the filter will not return any polygons that the character cannot traverse.