I am developing a simple application using libgdx and the Bullet API. I have completed the basic prototype of this application using shapes but now I want to load the real models in the application. I have used the **.g3db file** for loading the models through **AssetManager**

```
private void doneLoading() {
        // TODO Auto-generated method stub
        Model model = manager.get("ping1.g3db", Model.class);
        int index = 0;
        for (int i = 0; i < model.nodes.size; i++) {
            String id = model.nodes.get(i).id;
            ModelInstance instance = new ModelInstance(model, id);
            Node node = instance.getNode(id);
            instance.transform.set(node.globalTransform);
            //node.translation.set(0, 0, 0);
            //node.scale.set(1, 1, 1);
            //node.rotation.idt();
            instance.calculateTransforms();

            if (id.equals("ball4") || id.equals("bat")) {
                instance_array.add(instance);
                index += 1;
            }

            if (id.equals("ball4")) {
                ball = instance;
                Gdx.app.log("Ball Index", " " + index);
                instance_map.put("ball", new GameObject.Constructor(model, id, new btSphereShape(0.165f), 1.0f));
                createBall();
                //ball.transform.setToTranslation(0f, 10f, 0f);
            } else if (id.equals("bat")) {
                Gdx.app.log("Bat Index", " " + index);
                bat = instance;
                instance_map.put("bat",new GameObject.Constructor(model, id, new btSphereShape(1.897f), 0.0f));
                createBat();        
            }
        }
        loading = false;
    }

private void createBat() {
        // TODO Auto-generated method stub
        GameObject object=instance_map.get("bat").construct();
        object.body.setCollisionFlags(object.body.getCollisionFlags()|btCollisionObject.CollisionFlags.CF_CUSTOM_MATERIAL_CALLBACK);
        instances_gameobject.add(object);
        dynamicWorld.addCollisionObject(object.body);
    }

    private void createBall() {
        // TODO Auto-generated method stub
        GameObject object=instance_map.get("ball").construct();
        Gdx.app.log("Ball", "Ball created");
        object.moving=true;
        object.body.setWorldTransform(object.transform);
        object.body.setCollisionFlags(object.body.getCollisionFlags()|btCollisionObject.CollisionFlags.CF_CUSTOM_MATERIAL_CALLBACK);
        instances_gameobject.add(object);
        dynamicWorld.addCollisionObject(object.body);
    }

```

Please tell how could I use the custom models for collision detection.