datastructure_1.py

import os, compas, random
from compas.datastructures import Mesh
from compas_plotters import MeshPlotter

HERE = os.path.dirname(__file__)
DATA = os.path.join(HERE, 'data')
FILE = os.path.join(DATA,'faces.obj')

mesh = Mesh.from_obj(FILE)
plotter = MeshPlotter(mesh)

l = mesh.vertices_on_boundaries()
# get only boundary vertices without corners and flattening list of lists to list
boundary_vertices = [item for sublist in l for item in sublist if mesh.vertex_degree(item) == 3]

start_vertex_index = random.randint(0,len(boundary_vertices)-1)
start_vertex_key = boundary_vertices[start_vertex_index]

# only for quadmesh
def get_traverse(start_key):

    if start_key not in boundary_vertices:
        raise ValueError('Vertex not on boundary')
    if mesh.vertex_degree(start_key) == 2:
        raise ValueError('Vertex cannot be corner')
    
    vertices = [start_key]
    for key in mesh.vertex_neighbors(start_key):
        if mesh.vertex_degree(key) == 4:
            current = key
            break

    previous = start_key

    while True:
        vertices.append(current)
        if mesh.vertex_degree(current) < 4:
            break
        
        neighbors = mesh.vertex_neighbors(current, ordered=True)
        i = neighbors.index(previous)
        previous, current = current, neighbors[i-2]

    return vertices

traverse_vertices = get_traverse(start_vertex_key)
#print(traverse_vertices)

plotter.draw_vertices(
    facecolor={key: (255,0,0) for key in traverse_vertices},
    text= {key: str(key) for key in mesh.vertices()},
    radius=0.2
)

plotter.draw_edges(
    #color={key: (255,0,0) for key in traverse_edges},
)

plotter.show()