Calibration techniques for projector-based displays typically require that the display configuration remain fixed, since they are unable to adapt to changes such as the movement of a projector. In this paper, we present a technique that is able to automatically recalibrate a projector in real time without interrupting the display of user imagery. In contrast to previous techniques, our approach can be used on surfaces of complex geometry without requiring the quality of the projected imagery to be degraded. By matching features between the projector and a stationary camera, we obtain a new pose estimate for the projector during each frame. Since matching features between a projector and camera can be difficult due to the nature of the images, we obtain these correspondences indirectly by first matching between the camera and an image rendered to predict what the camera will capture.