I would like to test the beta version. I sent you PM I have Samsung Galaxy S3

Really nice!! Looking forward at beta release!

For graphics part is used only FrameBuffer.blit(...), but control of menu itself is little bit complex. I am used recursive algorithm.

Or you can get inspired by my GUI (maybe it will be sometimes for download...)

But for physic calculation it does very big difference.

I do not know if there is any better solution, but I render scene into npot texture and texture into screen. I am using post-processing effects, so it has no any negative impact on performance.

Probably you mean billboarding. If you need "lock" rotation in x and y axes of object, there is implemented method setBillboaring(boolean), but if you need only one axis, you have to implement it by your self.

No, non orthogonal transformation is for example scale in x axis

Calculation normals from modelViewMatrix is faster and for orthogonal transformations it is fine (transpose and invert is about O(300))

You do not need IPostProcessor. Render your scene into render target and in the next rendering you can do whatever.

http://www.jpct.net/jpct-ae/doc/com/threed/jpct/FrameBuffer.html#setRenderTarget(int)

"Height map" is specular map

Are these models black? You can try to call cube.calcTextureWrap(), if it helps your models have no texture coordinates.

cube.setTexture("sand");

Yes of course, this is way how to do it more difficult.

You can get java sources of any application. It is good to know when you want to sell your app.