The goal of this paper is to introduce a surface tracking algorithm of 26-connected objects and to apply it to contour tracking of discrete 3D digital objects. We show that border notion is insufficient to make a distinction between outer points and points of its cavities. Then, we introduce 3D discrete surfaces modelization. A classical surface tracking algorithm is introduced for 6 and 18-connected objects. We propose an original contour tracking algorithm based on the surface tracking one, and an extension to 26-connected objects. Two parallelization strategies of the contour extraction algorithm are then proposed, one using a data structure of list, the other one, a spatial distribution of the image over the processors.