1. crop_point_cloud

关键函数

chair = vol.crop_point_cloud(pcd)   # vol: SelectionPolygonVolume

import open3d as o3d

if __name__ == "__main__":
    # 1. read pcd
    print("Load a ply point cloud, crop it, and render it")
    sample_ply_data = o3d.data.DemoCropPointCloud()
    pcd = o3d.io.read_point_cloud(sample_ply_data.point_cloud_path)

    # 2. crop
    # vol: SelectionPolygonVolume, 定义裁剪区域
    vol = o3d.visualization.read_selection_polygon_volume(sample_ply_data.cropped_json_path) 
    chair = vol.crop_point_cloud(pcd)

    # 2. view
    # Flip the pointclouds, otherwise they will be upside down.
    pcd.transform([[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, -1, 0], [0, 0, 0, 1]])
    chair.transform([[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, -1, 0], [0, 0, 0, 1]])

    print("Displaying original pointcloud ...")
    o3d.visualization.draw([pcd])
    print("Displaying cropped pointcloud")
    o3d.visualization.draw([chair])

2. crop

pcd_cropped = pcd.crop(bbox)  # pcd: PointCloud. bbox: AxisAlignedBoundingBox

AxisAlignedBoundingBox https://blog.csdn.net/jizhidexiaoming/article/details/130561514?spm=1001.2014.3001.5501

# 1. read pcd
print("Load a ply point cloud, crop it, and render it")
sample_ply_data = o3d.data.DemoCropPointCloud()
pcd = o3d.io.read_point_cloud(sample_ply_data.point_cloud_path)

# 2. 定义裁剪区域。沿着y轴过滤: 只返回y坐标在[0.1,2]之间的点
bounds_list = [[-math.inf, math.inf], [0.8, 2], [-math.inf, math.inf]]  # xyz边界范围
# list2tuple, limit points边界点。itertools.product排列笛卡尔乘积是x,y,z各取一个值，组成xyz点坐标
bbox_pt_list = list(itertools.product(*bounds_list))
bbox_pt_vec = o3d.utility.Vector3dVector(bbox_pt_list)  # list
bbox = o3d.geometry.AxisAlignedBoundingBox.create_from_points(bbox_pt_vec)

# 3. crop
pcd_cropped = pcd.crop(bbox)

# 4. display
# Flip the pointclouds, otherwise they will be upside down.
pcd_cropped.transform([[1, 0, 0, 0], [0, -1, 0, 0], [0, 0, -1, 0], [0, 0, 0, 1]])
o3d.visualization.draw(pcd_cropped)

3. crop_mesh

上面是裁剪PointCloud，这里裁剪TriangleMesh.

转成numpy，修改mesh的traingles和triangle_normals成员。

import open3d as o3d
import numpy as np
import copy

if __name__ == "__main__":
    # 1. read mesh
    knot_mesh = o3d.data.KnotMesh()
    mesh = o3d.io.read_triangle_mesh(knot_mesh.path)
    mesh.compute_vertex_normals()
    print("Displaying original mesh ...")
    o3d.visualization.draw([mesh])

    # 2. crop: triangles and triangle_normals
    print("Displaying mesh of only the first half triangles ...")
    mesh_cropped = copy.deepcopy(mesh)  # mesh_cropped.triangles. (num, 3)
    mesh_cropped.triangles = o3d.utility.Vector3iVector(  # triangles
        np.asarray(mesh_cropped.triangles)[:len(mesh_cropped.triangles) // 2, :])
    mesh_cropped.triangle_normals = o3d.utility.Vector3dVector(  # triangle_normals
        np.asarray(mesh_cropped.triangle_normals)
        [:len(mesh_cropped.triangle_normals) // 2, :])
    print(mesh_cropped.triangles)
    o3d.visualization.draw([mesh_cropped])