Integration of Real and Virtual Light Sources in Augmented Reality Worlds

A number of issues need to be taken into consideration for the output of an augmented reality application to appear realistic. Such issues include the level of detail of the virtual scene, the accuracy of alignment between the two worlds and the correspondence of illumination between the real and virtual components. This paper reviews geometric registration techniques that are commonly used to perform the alignment process and photometric registration techniques that match illumination conditions. A research project that investigates both geometric and photometric registration is discussed. Although a number of geometric registration techniques exist, feature based methods have not yet achieved popularity within production environments because of the associated difficulties. Instead, fiducial marker based systems are being implemented for their robustness and ease of implementation. Many photometric registration techniques require pre-calibration or extensive CPU time. Very few operate in real-time and are compatible with geometric techniques. Further work to be undertaken is discussed towards the end of the paper.