This manuscript reports a geometrical and a topological methods to segment a closed triangular 2-manifold mesh M⊂ R3. The mesh M does not self-intersect) and has no border (ie watertight. Geometrical and topological segmentation methods require a Boundary Representation (BRep) from M. Building the BRep for M uniforms the triangle orientations, and makes explicit triangle and edge-counter edge adjacency. In the context of Reverse Engineering, the sub-meshes produced by the segmentation are subsequently used to fit parametric surfaces, which are in turn trimmed by the sub-mesh boundaries (forming FACEs). A Full Parametric Boundary Representation requires a seamless set of FACEs, to build watertight SHELLs. The fitting of parametric surfaces to the triangular sub-meshes (ie sub-mesh parameterization) requires quasi-developable sub-meshes.