preprocessing_data.py

def find_neighbor(faces, faces_contain_this_vertex, vf1, vf2, except_face):
    for i in (faces_contain_this_vertex[vf1] & faces_contain_this_vertex[vf2]):
        if i != except_face:
            face = faces[i].tolist()
            face.remove(vf1)
            face.remove(vf2)
            return i

    return except_face

# Enter the file input path

mesh = pymesh.load_mesh(file)

# get elements
vertices = mesh.vertices.copy()
faces = mesh.faces.copy()    

# move to center
center = (np.max(vertices, 0) + np.min(vertices, 0)) / 2
vertices -= center


# get normal vector
mesh = pymesh.form_mesh(vertices, faces)
mesh.add_attribute('face_normal')
face_normal = mesh.get_face_attribute('face_normal')


# get neighbors
faces_contain_this_vertex = []
for i in range(len(vertices)):
    faces_contain_this_vertex.append(set([]))
centers = []
corners = []
for i in range(len(faces)):
    [v1, v2, v3] = faces[i]
    x1, y1, z1 = vertices[v1]
    x2, y2, z2 = vertices[v2]
    x3, y3, z3 = vertices[v3]
    centers.append([(x1 + x2 + x3) / 3, (y1 + y2 + y3) / 3, (z1 + z2 + z3) / 3])
    corners.append([x1, y1, z1, x2, y2, z2, x3, y3, z3])
    faces_contain_this_vertex[v1].add(i)
    faces_contain_this_vertex[v2].add(i)
    faces_contain_this_vertex[v3].add(i)

neighbors = []
for i in range(len(faces)):
    [v1, v2, v3] = faces[i]
    n1 = find_neighbor(faces, faces_contain_this_vertex, v1, v2, i)
    n2 = find_neighbor(faces, faces_contain_this_vertex, v2, v3, i)
    n3 = find_neighbor(faces, faces_contain_this_vertex, v3, v1, i)
    neighbors.append([n1, n2, n3])

centers = np.array(centers)
corners = np.array(corners)
faces = np.concatenate([centers, corners, face_normal], axis=1)
neighbors = np.array(neighbors)

# Root for saving the npy file

np.savez(root + '.npz',faces=faces, neighbors=neighbors)