Fig. 5.

Local Surface Patch (LSP), P_i with pairwise points (p_i, p_j) as part of a surflet-pair relation for (p_i, n_i) and (p_j, n_j), with p_i being the origin. θ and φ are the angles of vectors projection about the origin, p_i. θ is the projection angle from vector 〈p_i − p_j〉 to vector 〈p_i − p_c〉 while φ is the projection angle from vector 〈p_i − p_j〉 to vector 〈p_i − l〉. The LSP centre is given by p_c, keypoint is given as $p_{k_i}$ where i = 2. Finally, l is the vector position of $p_{k_i}-p_c$ [34].