TransformVertices crash

[Immortal Carp]

Hi. Sorry for my english but i think you will understand 

i'm working on augmented reality application, where i have four instances of Object3D and they are added/removed from world according to state of image fom camera. Problem is that the application sometimes crashes on onDrawFrame() method and I can't  find out why.

There is a log(it is allways the same)
FATAL EXCEPTION: GLThread 42496
java.lang.RuntimeException: [ 1414843865465 ] - ERROR: java.lang.NullPointerException
   at com.threed.jpct.Object3D.transformVertices(Object3D.java:5879)
   at com.threed.jpct.World.renderScene(World.java:1070)
   at com.example.app.views.AppRenderer.onDrawFrame(AppRenderer.java:84)
   at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1531)
   at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1248)
   at com.threed.jpct.Logger.log(Logger.java:193)
   at com.threed.jpct.Logger.log(Logger.java:150)
   at com.threed.jpct.World.renderScene(World.java:1085)
   at com.example.app.views.AppRenderer.onDrawFrame(AppRenderer.java:84)
   at android.opengl.GLSurfaceView$GLThread.guardedRun(GLSurfaceView.java:1531)
   at android.opengl.GLSurfaceView$GLThread.run(GLSurfaceView.java:1248)

and there is code of onDrawFrame() method:

Code Select Expand

@Override
public void onDrawFrame(GL10 gl) {
while (!CameraModel.getInstance().mBackgroundLoaded) {
Thread.yield();
}
fb.clear(back);
CameraModel model = CameraModel.getInstance();
mBackgroundTex.overrideTexelData(model.getBackground());
fb.blit(mBackgroundTex, 0, 0, 0, 0, (int) model.mPow2width,
(int) model.mPow2Height, model.mCamWidth, model.mCamHeight, -1,
false);
world.renderScene(fb); //app crashes on this line
world.draw(fb);
fb.display();
if (mSaveScene) {
int[] array = fb.getPixels();
IntBuffer dst = IntBuffer.wrap(array);
dst.rewind();
Bitmap bmp = Bitmap.createBitmap(fb.getWidth(), fb.getHeight(),
Bitmap.Config.ARGB_8888);
bmp.copyPixelsFromBuffer(dst);
saveScene(bmp);
mSaveScene = false;
}
}
Adding and removing object:

Code Select Expand

public void addObject(Object3D obj) {
world.addObject(obj);
}

public void removeObject(Object3D obj) {
world.removeObject(obj);
}

this happening in openGL thread

Have you any ideas what I'm doing wrong ?
Thanks

[EgonOlsen]

The reason in 99.9% of these cases is that rendering and adding/removing of objects don't happen in the same thread. In your case, you state that add and remove happen in openGL thread, but i'm not sure what you mean by that. They clearly don't happen in onDrawFrame, which is the place in which they should happen. Either that, or synchronize them with onDrawFrame.

[Immortal Carp]

Yes sorry I forgot.  Previously in onDrawFrame was happening all image analysis but I changed it and there is small chance that the analysis will be shorter than drawing.
Thank you. 

[EgonOlsen]

No problem. Just never rely on timing when synchronizing multiple threads, because even if it doesn't happen today, the next os version, runtime or device will break your app.