One possible extension to the system is to reduce the amount of prior knowledge of the light sources required by the system. A combination of partial information and image hints may be used in concert to determine the sun's location. The partial knowledge would introduce constraints on the possible locations, reducing the difficulty and improving the accuracy of an image based estimate. Light determination based on the image and user hints within the image is also conceivable, given that the user already provides large amounts of input to the system throughout the modeling process.
The system currently does not attempt to handle specular reflections, such as those generated by the sun reflecting off windows. These specularities provide hints as to the light source location. They should also be ignored in the image manipulation process, because they violate the lambertian reflectance assumption. However, the fact that a surface is specular should be remembered in some way, because specularities are likely to be important features in any re-rendering of the model.
The additions made to the Facade system currently do not include an interactive interface for specifying lighting information. Such an interface should be added.
The lighting calculations currently do not interact with the depth dependent texture mapping that Facade is capable of performing. In essence, the system is capable of generating disparity maps for a given face. These maps express the difference between the true surface and the modeled surface. In theory this information could be incorporated into the lighting model reconstruction process. They are also of possible importance in the re-rendering process. Of particular importance are self shadowing effects, such as those from shingled walls, which may have a significant impact on the apparent luminance of a surface.
Given the existence of lighting neutral texture maps that our methods produce, it is now possible to export a general purpose graphical model of the building for use in any simulation environment. Such models could be used to construct a virtual city, putting all the famous architecture of the world on one street.