This paper presents a new technique for approximating range images by means of adaptive triangular meshes with a bounded approximation error and without applying optimization. This new approach consists of three stages. In the first stage, every pixel of the given range image is mapped to a 3D point defined in a reference frame associated with the range sensor. Then, those 3D points are mapped to a 3D curvature space. In the second stage, the points contained in this curvature space are triangulated through a 3D Delaunay algorithm, giving rise to a tetrahedronization of them. In the last stage, an iterative process starts digging the external surface of the previous tetrahedronization, removing those triangles that do not fulfill the given approximation error. In this way, successive fronts of triangular meshes are obtained in both range image space and curvature space. This iterative process is applied until a triangular mesh in the range image space fulfilling the given approximatio...