jMonkeyEngine.org

Well as the comparision says, JME3 is able to load models in a sepreate thread, so my main question is what do I have to take care of when doing it this way?

My idea is just that I have some kinda  of background loader that I can pass a modelname + a node that should it be attached. Then the game continues while the Background loads the model, once finished it should be added to the node passed.

Possible problems I see
1. Loading textures/shaders for the model might result in problems (at least it did in JME2 it should work now i guess)
2. Attaching the child out of another Thread directly into the node might cause problems if it is rendering at the smae time?
3. The first frame the model appears a lag happens when the textures are uploaded to the opengl vram.

Any tips, ideas would be appreciated

I was able to load models with textures etc. on a different thread in jme2 already..

You can load textures from another thread, but you can't load them from multiple threads simultaneously, since TextureManager is not thread-safe in jME2.
I have recently commented out the multithreaded-based loading in jME3, it became incompatible to the many changes that happened with asset handling. The best way to do it is probably to have a preload list, that tells all resources that shall be loaded, then these resources are loaded in multiple threads depending on how many cores the machine has, you would then receive notifications in the OpenGL thread telling you that a resource has finished loading and needs handling.

MikOfClassX said:
I would really like to switch all my current JME2 based work (3D broadcast video engine) to JME3 but I feel it's a bit too fresh. I don't know.

Yes, jme3's structure is still not set in stone, so basing a project on it right now is not really recommended. But if you try around with it.. any feedback is very welcome and will help get jme3 out sooner.

Well actually just do the loadmodel path in a second thread, and then attach it in the opengl thread.
I strongly suggest learning a bit more about threading and synchronizing however before as you will make mistakes otherwise.

If you can read german I could give you some stuff where it is explained, other wise you have to search yourself

java concurrency

You can assetManager.loadModel() on a separate thread, then you only have to attach the model on the OpenGL thread like this:

Future fut = application.enqueue(new Callable() {
    public Object call() throws Exception {
        //this is where you modify your object, you can return a result value
        return modifyObject();
    }
});

//to retrieve return value (waits for call to finish, fire&forget otherwise):
fut.get();

public class AssetLoader extends Thread
{
private AssestManager am;

public AssetLoader(AssestManager assetm)
{
am = assetm;
}
public void run()
{
am.loadModel() // replace with real code
}

}

Then in your game code

public mygame extends SimpleApplication
{
....
AssetLoader al = new AssetLoader(assetmanager);
al.start();
...
}

thats not the only way to make new threads. you really need to read up on the subject.
http://www.javaworld.com/jw-04-1996/jw-04-threads.html