Chi Chang and Yu-Tai Ching
Department of Information and Computer Science
National Chiao Tung University
Hsinchu, Taiwan R.O.C.
In this work, we attempt to produce a shading image from a shade image under a different light source direction. In computer graphics, the surface normal is the most important element for shading. We study the possibility of recovering the surface normal from the shaded images. We report in this paper that if there are at least three images, by applying the finite difference method without assigning initial values, we can reconstruct the surface normal very well. Experiments have been carried out on synthesized images and real images. The results show that the reconstructed surface normal for both synthesized images and real images is good enough for the applications in computer graphics.
Keywords: computer graphics, phong shading, image processing, photometric sampling, finite difference method
Received December 30, 1993; revised September 24, 1995.
Communicated by Chuan-lin Wu.
*This work was sssupport in part under NSC-81-0408-E009-208 and NSC-81-0408-E009-534, the National Science Council, Taiwan, R.O.C.