[SOLVED] Using TerrainQuad.getHeight() properly

Troubleshooting terramonkey
1

I am trying to generate a bunch of plant models at random spots on the surface of the terrain but terrainQuad.getHeight(); isn’t returning the correct value; at least it’s not returning the value that my character’s local translation is returning.

This is the code I am using:

 gameLevel = app.getAssetManager().loadModel("Scenes/FirstScene.j3o");
        gameLevel.setLocalScale(5);
        gameLevel.addControl(new RigidBodyControl(0));
        this.app.getRootNode().attachChild(gameLevel);
        bulletAppState.getPhysicsSpace().addAll(gameLevel);
      
       terrainGeo = gameLevel;
       terrainQuad = ((TerrainQuad)((Node)terrainGeo).getChild("terrain-FirstScene"));
       Node plantcube = (Node) app.getAssetManager().loadModel("Models/plantcube.j3o");
       List<Node> lilys = new ArrayList<>();
       
       for(int i=0;i<2000;i++){
            lilys .add((Node) plantcube.clone());
                                                 }
       for (Node lily: lilys) {
            float a = (float) Math.random()*2000;
            float c = (float) Math.random()*2000;
         lily.setLocalTranslation(-1000 + a,  terrainQuad.getHeight(new Vector2f((-1000 + a),(-1000+c))),-1000 +c);
         lily.setLocalRotation(new Quaternion(0.0f, 0.93807447f + (float)Math.random(), 0.0f, -0.34643376f+ (float)Math.random()));
         this.app.getRootNode().attachChild(lily);
                                             }

This is what it looks like:
https://puu.sh/BFfQP/d7df917089.png
What’s especially vexing to me is that the difference between the models local translation.y and the terrainquad.getHeight isn’t constant.

2

I ran into a similar issue in the past, and I recall getting things to work when I switched to use the .getHeightmapHeight() method instead of .getHeight()

Unless I’m mistaken, it looks like you’re inputting world coordinates to the .getHeight() method, and I believe that method actually takes in the local coordinates for the TerrainQuad.
https://javadoc.jmonkeyengine.org/com/jme3/terrain/geomipmap/TerrainQuad.html#getHeight-com.jme3.math.Vector2f-

And then the .getHeightMapHeight() method takes in world coordinates.
https://javadoc.jmonkeyengine.org/com/jme3/terrain/geomipmap/TerrainQuad.html#getHeightmapHeight-com.jme3.math.Vector2f-

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3

Ok so, you are definitely correct that I should be using getHeightmapHeight(). I just created another Scene and Terrain within it using one of the JME random hill terrain generators and now everything is working properly…unfortunately I don’t want to just give up the Scene i’ve been working on for a while. Any idea what properties of a Terrain would cause it to behave like that?

I altered the mesh of the “Original” Terrain that was having heightmap problems using the JME3 Terrain Editor.

4

Hmm I’m not entirely certain, but did you alter the mesh by using the terrainQuad.setHeight(Vector2f coord, float height); method, or by altering the mesh’s vertex buffer. I think altering the vertex buffer could cause the problem, since that would not alter the height map data being stored in the TerrainQuad class, only the mesh.

Edit: my bad, I just saw you did mention that you altered the terrain using the terrain editor. I’m not quite sure what could have been the cause then, I use the terrain editor a lot as well but haven’t noticed that problem. Did you possibly scale the terrain when it was having issues? I think one of the javadocs mentioned that the getHeight() methods don’t take scaling into account.

Another potential factor could be if your’e attaching more than one LOD control - the terrain editor will create an LOD control for you by default when you make a new Terrain, and then I’ve also had times where I accidentaly added a second LOD Control at run-time and I got some weird results.

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5

I’m an absolute buffoon; there was a minuscule rotation quaternion being applied to the scene. Thanks for your help!

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6

Also, as a final note to anyone looking at this in the future, if you use TerrainQuad.getHeight(), it properly takes into account both Scene scaling as well as Terrain scaling! TerrainQuad.getHeightmapHeight() does not.

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7

Glad to hear you got things working :slightly_smiling_face:

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