如何将 3D 点云 (.ply) 转换为网格(带有面和顶点)

Question

我有一个包含 100 万个点的 3-D 点云文件，我需要将其转换为 trimesh 中的网格文件。这里的最终目标是获取一个点云并确定该点云是凸的还是凹的(trimesh 允许我在将云转换为网格后做到这一点(。我愿意让其他图书馆解决这个问题。

我已经尝试过使用 scipy 的 Delaunay 三角测量，我似乎无法将我的点云转换为正确的格式，以便 trimesh 可以读取它。

import open3d as o3d
import numpy as np
import trimesh
from scipy.spatial import Delaunay

pointcloud = o3d.io.read_triangle_mesh("pointcloud.ply")
points = np.array(pointcloud.points)
triangle_mesh = Delaunay(points)
#  How do i include triangle_mesh from Delaunay triangulation into processing the mesh file?
mesh = trimesh.load("pointcloud.ply")
print(trimesh.convex.is_convex(mesh))

错误

geometry::TriangleMesh appears to be a geometry::PointCloud (only contains vertices, but no triangles).
geometry::TriangleMesh with 1390073 points and 0 triangles.
expected = (faces.shape[0], faces.shape[1] * 2)
AttributeError: 'NoneType' object has no attribute 'shape'

Answer 1

Open3d 0.8.0.0 现在已经实现了滚球旋转算法，以从点云重建网格。

我使用以下方法解决了从点云生成三网格的问题：

import open3d as o3d
import trimesh
import numpy as np
pcd = o3d.io.read_point_cloud("pointcloud.ply")
pcd.estimate_normals()
# estimate radius for rolling ball
distances = pcd.compute_nearest_neighbor_distance()
avg_dist = np.mean(distances)
radius = 1.5 * avg_dist   
mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_ball_pivoting(
           pcd,
           o3d.utility.DoubleVector([radius, radius * 2]))
# create the triangular mesh with the vertices and faces from open3d
tri_mesh = trimesh.Trimesh(np.asarray(mesh.vertices), np.asarray(mesh.triangles),
                          vertex_normals=np.asarray(mesh.vertex_normals))
trimesh.convex.is_convex(tri_mesh)

Answer 2

只是询问这行代码实际上做了什么？它调用带有点云的函数，如pcd，但双向量部分是什么意思？- o3d.utility.DoubleVector([radius, radius * 2]))

mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_ball_pivoting(
           pcd, o3d.utility.DoubleVector([radius, radius * 2]))

Answer 3

在以下答案后保存网格https://stackoverflow.com/a/57971745/6394769 使用三网格导出选项：

trimesh.exchange.export.export_mesh(tri_mesh, 'output file path.ply .obj etc..')

https://trimsh.org/trimesh.exchange.ply.html

如果要在三目中保留颜色，请进行以下更改：

tri_mesh = trimesh.Trimesh(....., vertex_colors = np.asarray(mesh.vertex_colors))

https://trimsh.org/trimesh.base.html

或者，您可以使用open3d本身直接保存网格：

o3d.io.write_triangle_mesh('file path .ply or .obj etc..', mesh, write_ascii=True (if needed as text and not binary file), compressed=False, print_progress=False)

如果网格变量中存在网格颜色，则网格颜色也保存在此处。

http://www.open3d.org/docs/release/python_api/open3d.io.write_point_cloud.html#open3d.io.write_point_cloud