Real!

The live action was shot with a modified version of the proprietary digital 3-D Fusion Camera System, developed by Cameron and Vince Pace.

During filming, Cameron made use of his virtual camera system, a new way of directing motion-capture filmmaking.

To film the shots where CGI interacts with live action, a unique camera referred to as a "simulcam" was used, a merger of the 3-D fusion camera and the virtual camera systems. While filming live action in real time with the simulcam, the CGI images captured with the virtual camera or designed from scratch, are superimposed over the live action images as inaugmented reality and shown on a small monitor, making it possible for the director to instruct the actors how to relate to the virtual material in the scene.

It is an interface that allows differ apps to share ur webcam

With a camera.