def _accumulate_normals(tris, tri_nn, npts):
 nn = np.zeros((npts, 3))
 for verts in tris.T:
  for idx in range(3):
   nn[:, idx] += np.bincount(verts, weights=tri_nn[:, idx], minlength=npts)
 return nn

def _accumulate_normals ( tris , tri_nn , npts ) : nn = np . zeros ( ( npts , 3 ) ) for verts in tris . T : for idx in range ( 3 ) : nn [ : , idx ] += np . bincount ( verts , weights = tri_nn [ : , idx ] , minlength = npts ) return nn
efficiently accumulate triangle normals .