Processing is a programming language, library, and environment for visual artists, designers, and programmers. Here is an example of an Android app I wrote using Processing to demonstrate work I did to merge the Processing for Android library with the Google Cardboard SDK. Now you can write Cardboard VR apps using Processing.
This open source code can be found at: https://github.com/ajavamind/Processing-Cardboard
The example code builds the demonstration app above that displays a stereo photo cube in front of a stereo photo background. In a Cardboard viewer the user may change the viewing angle and size of the cube with head movement. A screen tap will bring the cube back to its original viewing location. Tilting the viewer left or right will change the cube size. Moving your finger on the display will rotate the cube for a different view.