In many modeling or shape processing applications, the representation of 3D objects as a collection of voxels is an interesting alternative that offer several advantages: some volumetric operations become trivial and the regular lattice allows us to represent complex geometries in a very efficient way. However, when some performing geometry processing tasks on the voxel set surface, this model requires to revisit some geometry processing tools and theorems. In this presentation, we focus on the stability (multigrid convergence) of some differential estimators (normal vector fields, curvature tensor, Laplace-Beltrami operator...). Joint work with Thomas Caissard (Lyon), Jacques-Olivier Lachaud (Chambéry) and Tristan Roussillon (Lyon)