Can you configure a viewport so that it shows only a part of the image from the associated camera (for example, show the upper left quarter).
Part of what image? Do you mean scene? What quarter?
I think you’ve got a terminology problem here. :?
You’ll have to explain things in another way.
If you want your viewport smaller, have a look at TestMultiViews in the jMETests project
Sorry for the terminology, I’m new to this. I know how to ajust the size of the viewports, but they will always show the same thing, larger or smaller. I want to cut off what the viewport is showing, and show only one part of the visual field. For you to understand I’ll tell you the way I accomplished a similar effect: I redefined the frustum. There is a problem in doing that, since in my application I’d need an assymetric frustum. When doing that, some objects dissapeared even if they were inside the frustrum. I found on this post http://hub.jmonkeyengine.org/groups/contribution-depot-jme2/forum/topic/problem-using-asymetric-frustum/ that the frustrum implementation is buggy. Do you know any other thing I could do to achieve the same effect? By now I can only overlap the different viewports so that the hide the part I don’t want to show, it works but doesn’t sound good.
If you want to know, for an autostereoscopic device, I need to interleave vertical stripes that alternate the angles of the two cameras. My idea was to use one viewport for every stripe, and managing the part they show with the frustum (since I don’t see documentation on stencils, what might be a good idea). Maybe there is a totally different way to face the problem.
Thanks a lot!!!
(I can print screen if you want to)
Somebody in the forum suggested me to use a shadder to combine the two images. I’m giving a try to it 
Upon some testing I concluded the patch is indeed correct. It has now been applied 
So you can now freely use asymmetric frustums in your application