Abstract: A surface reconstruction algorithm in CAD is used on the basis of three-dimensional shape from shading. First, use the physical surface imaging model to create a reflection map equation based on Lambertian reflectance model; second, use the finite difference method to scatter approximation of the surface gradient to obtain the function equation of the physical surface; then find its solution by using of Netwon-Raphson iterative method to obtain the function value of the reconstructed surface height. the reconstruction results in line with product model data transferring standards and then the exchange in CAD system is realized. The image restoration through three-dimensional surface shape validates the feasibility of the algorithm and the reconstruction system.

Key words: shape from shading, CAD, finite difference, Lambertian reflectance model