Retrieval the Tilt Angle of Solar Illumination from a Single Architectural Photograph
基于单幅建筑物图像的太阳光方位角恢复

When users want to plan the reconstructed virtual scenes, if we obtained the information of the lighting at the time when the images were taken, we can use the rendering technologies from computer graphics to obtain new synthesized photorealistic imageries. This paper presents techniques for recovering the tilt angle of solar illuminant from a single outdoor building image, which can be integrated to most current image-base architectural rebuilding systems. Solar illumination can be treated as parallel light. Its direction can be measured by tilt and slant angle in architectural coordinate system. To calculate the tilt angle, we utilize the changes of intensities from different wall surfaces. This idea comes from SFS (Shape from Shading) technique. On the basis of the calculated tilt angle, we can easily calculate the slant angle from images by using the bulges of the wall surface and their shadows.