A Servocontrol-Based Augmented Reality Registration Method for Digital Reconstruction of Yuanmingyuan Garden

Registration in three dimensions is one of the most important and difficult issues in outdoor augmented reality system. A servocontrol-based registration method is designed for robust registration. The proposed method can improve the accuracy of the registration without the requirement for improving tracker itself. Taking the outdoor environment and requests of historical site reconstruction into account, inertial tracking is adopted for head tracking. With the orientation data obtained by inertial tracker, the real camera is controlled as a follow-up rotation. The real camera is fixed on a high speed rotational table which is driven by a stepping motor with a high precision. At the same time, the virtual camera in three-dimension virtual world is also controlled by the same orientation data. Thus, different from the conventional registration method, the servo-control system manages to avoid the influence of errors from tracker on the combination of virtual and real world. The building of camera model in virtual world, calibration of real camera and registration in rendering engine are also discussed. The error and time lag is tested by experiments. Experimental results show the improvements of the proposed method on stability and accuracy. The application of the proposed system in the digital reconstruction of Yuangmingyuan Garden indicates its potential to be used in real scene.