the concept is to create kinetic furniture that allows the user to communicate with virtual space.
What exactly is the user communicating with?
Presumably, and please correct me if I'm making any assumptions that are not in keeping with your unstated process, the data will be read by the Arduino, and sent to a PC.
Start by defining exactly what each potentiometer is going to do. Rotate about X? Rotate about Y? Rotate about Z? Zoom? Pan in X? Pan in Y? Pan in Z? To do all of these, you'd need as least 7 potentiometers.
i have created a 2d graph in processing using 1 potentiometer
What did the potentiometer control? X? Y?
Processing can be used to draw 3D objects, and manipulate the view of the object based on user (or serial) inputs. Look at the 3D + Camera + MoveEye example that rotates a cube based on the mouse position in Y. Extending that to rotate based on serial data would be trivial. Extending it to rotate in 2 directions based on 2 inputs is equally easy.
4 potentiometers is either more than you need, or less than you need. Whatever it is you need, though, you need to move the project from the art world to the engineering world. That involves requirements that can defined with your hands in your pockets.