Shadow synthesis in natural sequences using 3-D scene model

Abstract

This paper presents a new method which allows the artificial creation of cast shadows in the context of video post-production applications for which video objects are inserted in an original video sequence. The manipulated video objects are assumed to have been previously segmented together with their cast shadows in their original images, and to have been inserted in the edited images. This paper deals with the problem of the artificial creation of the corresponding cast shadows. A reference image which represents the scene illuminated background is assumed to be available. The proposed method is based on a precise shadow model and on the use of the 3-D structure of the scene background. This 3-D information is roughly obtained manually in a pre-processing phase. Then, the illumination conditions, i.e. a shadow model and the light source position are estimated. The shape and texture of the created cast shadows are defined by combining geometrical relations linking the light source, the video objects and the cast shadows, and by applying the inverse shadow model to artificially shade the shadow areas. Experimental results show that it is possible to obtain satisfactory visual results.