Disappearing nodes in SimpleCanvasImpl (probably frustum issue)

I searched the forums for an answer to my issue but I can't seem to get it working.

The problem:  I have a simple scene with a terrain block and two boxes.  There are two views, one from the perspective of each box.  As I am moving the boxes around, I find that at certain angle and distance combinations, one box disappears from the other's view.  If I turn back, it pops back into view.  So essentially, at certain distances, the other box is not visible on the edges of the other's view.  It's like there is no peripheral vision.

So I looked at some similar questions and I gathered this is generally a bounding volume or frustum issue.  I made sure my boxes had bounding boxes and also my root node.  That didn't make any apparent difference.  I started playing around with the camera (esp. frustum) but I get weird wide-angle effects and/or it doesn't fix the issue.

Should it be necessary to change anything with respect to the camera in a subclass of SimpleCanvasImpl?  If so, can anyone tell me what I am missing here or point me to something that will help me understand what would cause this?

thanks in advance.

Am I doing something wrong in the way I am asking this?  I can't imagine that no one is running into the same issue with SimpleCanvasImpl.

So I was wrong, it's not that they are disappearing on the edges of the view.  Well, they are but they also disappear when they are in the middle of the view and I move away.  They aren't very far.

I'm calling this in my set up:

cam.setFrustumPerspective(45.0f, (float) width / (float) height, 1f, 1000);

Which is what I think SimpleCanvasImpl does anyway.

I think I've done something that's causing this but I have no idea what.  It's not consistent either.  Everything will be fine for a while and then this will start happening.

OK, figured out the cause.  I changed the code to set the direction of the camera instead of the frame.  I looked at the implementation and it doesn't set the up or left of the camera.  Up doesn't change in my app (for now).

So, I still want to use the direction but I don't know what exactly I should set left to.  Any help is appreciated.

You can set left to the cross of your world up and your direction

Thanks again renanse.  That seems to have done it.