Strange error Savable

Troubleshooting General Help
1

Hello

So i was thinking about creating a save feature with Savable.
I already had a pretty big objectgraph so i let all the things implement Savable, and finally at the top an AppState, then i could in theory save and load the entire thing.

The serialization works (in XML form i can see that everything is there).
It loads without exceptions.
But when i attach the newly loaded AppState i get this:

java.lang.NullPointerException
at com.jme3.renderer.opengl.GLRenderer.clearVertexAttribs(GLRenderer.java:2322)
at com.jme3.renderer.opengl.GLRenderer.renderMeshDefault(GLRenderer.java:2674)
at com.jme3.renderer.opengl.GLRenderer.renderMesh(GLRenderer.java:2701)
at com.jme3.material.Material.renderMeshFromGeometry(Material.java:728)
at com.jme3.material.Material.render(Material.java:1217)
at com.jme3.renderer.RenderManager.renderGeometry(RenderManager.java:564)
at com.jme3.renderer.queue.RenderQueue.renderGeometryList(RenderQueue.java:266)
at com.jme3.renderer.queue.RenderQueue.renderQueue(RenderQueue.java:305)
at com.jme3.renderer.RenderManager.renderViewPortQueues(RenderManager.java:814)
at com.jme3.renderer.RenderManager.flushQueue(RenderManager.java:725)
at com.jme3.renderer.RenderManager.renderViewPort(RenderManager.java:1040)
at com.jme3.renderer.RenderManager.render(RenderManager.java:1088)
at com.jme3.app.SimpleApplication.update(SimpleApplication.java:260)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.runLoop(LwjglAbstractDisplay.java:151)
at com.jme3.system.lwjgl.LwjglDisplay.runLoop(LwjglDisplay.java:192)
at com.jme3.system.lwjgl.LwjglAbstractDisplay.run(LwjglAbstractDisplay.java:232)
at java.lang.Thread.run(Thread.java:745)

I tried to reproduce this in a little project but i cant get it to not work…lol
But the main project is too large to post here.
The structure goes like this:

AppState
—Node
—ArrayList
—some more primitive fields…

And in the List i have objects that contain more Savable’s as fields.

As soon as i attach the node in the AppState i get the exception.

So now i dont really ask for a concrete solution, just for any general direction where i should look for the solution.
(btw i dont even understand how this error can even happen)

Any tips or advice on how i could go and at least narrow down the problem would be great!

2

After some hours of debugging i finally got to the root of the problem.
Ive got a custom mesh and i saved it too. (I know i should not save them)
In my read method of that object i recreated the geometry and now it works correctly.

But the thing is that i saved this same mesh elsewhere and there it worked properly.

My point is: there may be an issue in saving custom meshes.

3

Well, there isn’t really any magic here, though. Your own methods are called to save and load it. When reading, JME creates a new instance, calls your method. So if it’s not reading it correctly then that’s the place to start.

4

My mesh is just a simple quad (the difference is it is centered at the origin)
It just simply sets up the buffers, and in XML form the buffers are there, so i think they should be read.
Am i right?

5

The code looks fine from here. So I don’t know.

Like, I’m not sure why you are creating geometry inside a mesh… but I can’t see the code so I’m speculating on a like 100 different things from your description.

Only code is real.

6

Sorry, i did not post because i did not know where the error came from but now i can show the essential part:

public abstract class GameObject implements Savable {

private static long id = 0L;

protected Node node;
protected Geometry geometry;
protected Vector2f position;
protected long ID;
protected float age;
protected boolean dead;

public GameObject() {
    ID = id++;
    dead = false;
}
...
    @Override
public void write(JmeExporter ex) throws IOException {
    OutputCapsule cap = ex.getCapsule(this);
    cap.write(node, "GONode", null);
    cap.write(geometry, "GOGeometry", null);
    cap.write(position, "GOPosition", null);
    cap.write(ID, "GOID", 0);
    cap.write(age, "GOAge", 0);
    cap.write(dead, "GODead", false);
}

@Override
public void read(JmeImporter im) throws IOException {
    InputCapsule cap = im.getCapsule(this);
    node = (Node) cap.readSavable("GONode", null);
    geometry = (Geometry) cap.readSavable("GOGeometry", null);
    position = (Vector2f) cap.readSavable("GOPosition", null);
    ID = cap.readLong("GOID", 0);
    age = cap.readFloat("GOAge", 0);
    dead = cap.readBoolean("GODead", false);
}

public final class Enemy extends GameObject implements EventHandler {
  @Override
  public void write(JmeExporter ex) throws IOException {
    super.write(ex);
    OutputCapsule cap = ex.getCapsule(this);
    cap.write(material, "EnemyMaterial", null);
    ...

  }

  @Override
  public void read(JmeImporter im) throws IOException {
    super.read(im);
    InputCapsule cap = im.getCapsule(this);
    hpbar_width = cap.readFloat("EnemyHPBarWidth", 0);
    ....

    Mesh m = new MyQuad();
    FloatBuffer tc = BufferUtils.createFloatBuffer(4 * 2);
    float w = (float) material.getParam("FrameWidth").getValue();
    tc.put(0).put(1);
    tc.put(0).put(0);
    tc.put(w).put(0);
    tc.put(w).put(1);
    m.setBuffer(VertexBuffer.Type.TexCoord, 2, tc);
    m.updateBound();
    geometry.setMesh(m);

  }
}

public final class MyQuad extends Mesh{

public MyQuad() {
    FloatBuffer vb = BufferUtils.createFloatBuffer(4 * 3);
    FloatBuffer tc = BufferUtils.createFloatBuffer(4 * 2);
    FloatBuffer nb = BufferUtils.createFloatBuffer(4 * 3);
    ShortBuffer ib = BufferUtils.createShortBuffer(6);
    vb.put(-0.5f).put(0).put(0.5f);
    vb.put(-0.5f).put(0).put(-0.5f);
    vb.put(0.5f).put(0).put(-0.5f);
    vb.put(0.5f).put(0).put(0.5f);
    ib.put((short)1).put((short)0).put((short)2);
    ib.put((short)2).put((short)0).put((short)3);
    tc.put(0).put(1);
    tc.put(0).put(0);
    tc.put(1).put(0);
    tc.put(1).put(1);
    nb.put(0).put(1).put(0);
    nb.put(0).put(1).put(0);
    nb.put(0).put(1).put(0);
    nb.put(0).put(1).put(0);
    vb.rewind();
    ib.rewind();
    tc.rewind();
    nb.rewind();

    setBuffer(VertexBuffer.Type.Position, 3, vb);
    setBuffer(VertexBuffer.Type.Index, 3, ib);
    setBuffer(VertexBuffer.Type.TexCoord, 2, tc);
    setBuffer(VertexBuffer.Type.Normal, 3, nb);

    updateBound();
}
}

These are the essential parts.
On top of this sits an appstate with a list of these:

ArrayList<GameObject> gameObjects = new ArrayList<>(100);

and saves them as so:

cap.writeSavableArrayList(gameObjects, "WorldStateGameObjects", null);

This way it works. Before, i was just letting the geometry come from the gameobject’s read.

7

So you’re showing me the working code?

Well, since you got it working somehow then I guess it doesn’t matter anyway… but to fix broken code we’d need to see the broken code.