Mixing video and computer-generated images is a new and promising area of research for enhancing reality. It can be used in all the situations when a complete simulation would not be easy to implement. Past work on the subject has relied for a large part on human intervention at key moments of the composition. In this paper, we show that if enough geometric information about the environment are available, then efficient tools developed in the computer vision literature can be used to build a highly automated augmented reality loop. We focus on outdoor urban environments and present an application for the visual assessment of a new lighting project of the bridges of Paris.