Cloud vertices, What is it ?

Basics

Cloud vertices is a synonym for point cloud. It is a group of points in a 3D space.

It can be initialized from:

• a list of vertices

• a numpy array (shape (N, 3))

• an Excel file

• a CSV file (with/without header)

• a Shape file (point type)

• a DXF file (MTEXT or INSERT)

Each point can have associated values.

Storage

All vertices are stored in a dictionnary. The main key is the index of the point in the list.

Each entry is a dictionnary with at least the following key : vertex (the wolf_vertex instance).

Other keys can be added to store additional information.

KD-tree

A KD-tree is a data structure that allows for efficient nearest neighbor searches in a multi-dimensional space. It is particularly useful for spatial queries, such as finding the closest points in a point cloud.

Each instance of cloud_vertices has a KD-tree associated with it. The KD-tree is built using the vertices of the point cloud, and it allows for fast nearest neighbor searches.

# import _add_path # this line can be deleted if wolfhece is installed as a package (-> debug mode only)

from wolfhece import __version__
assert __version__ > '2.2.8', f'Bad version of wolfhece: {__version__} <= 2.2.8'

from wolfhece.PyVertex import cloud_vertices, wolfvertex

import numpy as np

Create a new cloud_vertices instance

vertices = np.array([[0, 0, 0], [1, 1, 1], [2, 2, 2], [3, 3, 3], [4, 4, 4]])

cloud = cloud_vertices()

cloud.init_from_nparray(vertices)

# number of vertices
print(cloud.nbvertices)

# Header information
print(cloud.has_values)
print(cloud.header)

5
False
[]

Get coordinates of the vertices

xyz = cloud.xyz # -> np.ndarray with shape (n,3)

print(xyz)

[[0. 0. 0.]
 [1. 1. 1.]
 [2. 2. 2.]
 [3. 3. 3.]
 [4. 4. 4.]]

Add a value

new_val = np.array([1, 2, 3, 4, 5])

cloud.add_values_by_id_list('test', new_val)

print(cloud.header)

['vertex', 'test']

Get coordinates but value as z

xyz_val = cloud.get_xyz('test')

print(xyz_val)

[[0. 0. 1.]
 [1. 1. 2.]
 [2. 2. 3.]
 [3. 3. 4.]
 [4. 4. 5.]]

Find the nearest vertex

nb = 1
dist, vert, assoc_dict = cloud.find_nearest([[.5, .5, 0.]], nb= nb)

# If the number of neighbors is 1, the output is a single list of vertices and distances
# If the number of neighbors is greater than 1, the output is a list of lists of vertices and distances

print('distance:', dist)
print('vertex:', vert.x, vert.y, vert.z)
print('key:', assoc_dict)

distance: 0.7071067811865476
vertex: 0.0 0.0 0.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B1087DA4A0>, 'test': np.int64(1)}

Find the nearest vertices

nb = 2

nb = 2
dist, vert, assoc_dict = cloud.find_nearest(np.asarray([[.5, .5, 0.]]), nb= nb)

# If the number of neighbors is 1, the output is a single list of vertices and distances
# If the number of neighbors is greater than 1, the output is a list of lists of vertices and distances

print('number of neighbors:', len(dist))

for i in range(nb):
    print('distance:', dist[i])
    print('vertex:', vert[i].x, vert[i].y, vert[i].z)
    print('key:', assoc_dict[i])

number of neighbors: 2
distance: 0.7071067811865476
vertex: 0.0 0.0 0.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B1087DA4A0>, 'test': np.int64(1)}
distance: 1.224744871391589
vertex: 1.0 1.0 1.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B128E67DF0>, 'test': np.int64(2)}

Find the nearest vertex for multiple points

nb = 2
xyz1 = [.5, 1., 0.]
xyz2 = [.5, 2., 1.]
dist, vert, assoc_dict = cloud.find_nearest([xyz1, xyz2], nb= nb)

# If the number of neighbors is 1, the output is a single list of vertices and distances
# If the number of neighbors is greater than 1, the output is a list of lists of vertices and distances

if nb ==1:
    for i_vert in range(2):
        print('distance:', dist[i_vert])
        print('vertex:', vert[i_vert].x, vert[i_vert].y, vert[i_vert].z)
        print('key:', assoc_dict[i_vert])
else:
    for i_vert in range(2):
        for i in range(nb):
            dist_list = dist[i_vert]
            vert_list = vert[i_vert]
            assoc_dict_list = assoc_dict[i_vert]

            print('distance:', dist_list[i])
            print('vertex:', vert_list[i].x, vert_list[i].y, vert_list[i].z)
            print('key:', assoc_dict_list[i])

distance: 1.118033988749895
vertex: 1.0 1.0 1.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B128E67DF0>, 'test': np.int64(2)}
distance: 1.118033988749895
vertex: 0.0 0.0 0.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B1087DA4A0>, 'test': np.int64(1)}
distance: 1.118033988749895
vertex: 1.0 1.0 1.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B128E67DF0>, 'test': np.int64(2)}
distance: 1.8027756377319946
vertex: 2.0 2.0 2.0
key: {'vertex': <wolfhece.PyVertex.wolfvertex object at 0x000002B128E66350>, 'test': np.int64(3)}