Geometrical methods for dividing buildings by plane

city_model_structure/plying_with_geometry.py

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+import trimesh
+from trimesh import intersections as inter
+import open3d as o3d
+import numpy as np
+
+
+def extract_points(segment_list):
+  point_list = np.asarray(segment_list[0])
+  for segment in segment_list:
+    found = False
+    for new_point in segment:
+      for point in point_list:
+        comparison = new_point == point
+        if comparison.all():
+          found = True
+          break
+      if not found:
+        point_list = np.concatenate((point_list, [new_point]))
+  return point_list
+
+
+def point_cloud_to_mesh(point_list, normal_list):
+  pcd = o3d.geometry.PointCloud()
+  pcd.points = o3d.utility.Vector3dVector(point_list)
+  pcd.normals = o3d.utility.Vector3dVector(normal_list)
+  distances = pcd.compute_nearest_neighbor_distance()
+  avg_dist = np.mean(distances)
+  radius = 3 * avg_dist
+  bpa_mesh = o3d.geometry.TriangleMesh.create_from_point_cloud_ball_pivoting(
+           pcd,
+           o3d.utility.DoubleVector([radius, radius * 2]))
+  mesh_result = trimesh.Trimesh(vertices=np.asarray(bpa_mesh.vertices), faces=np.asarray(bpa_mesh.triangles))
+  return mesh_result
+
+
+def merge_meshes(mesh1, mesh2):
+  v_1 = mesh1.vertices
+  f_1 = mesh1.faces
+  v_2 = mesh2.vertices
+  f_2 = mesh2.faces
+  length = len(v_1)
+  v_merge = np.concatenate((v_1, v_2))
+  f_merge = np.asarray(f_1)
+
+  for item in f_2:
+    point1 = item.item(0) + length
+    point2 = item.item(1) + length
+    point3 = item.item(2) + length
+    surface = np.asarray([point1, point2, point3])
+    f_merge = np.concatenate((f_merge, [surface]))
+
+  mesh_merge = trimesh.Trimesh(vertices=v_merge, faces=f_merge)
+
+  return mesh_merge
+
+
+# example
+vertices = [[0, 0, 0], [0, 0, 1], [0, 1, 0], [0, 1, 1], [1, 0, 0], [1, 0, 1], [1, 1, 0], [1, 1, 1]]
+faces = [[0, 1, 2], [1, 3, 2], [1, 5, 3], [5, 3, 7], [0, 4, 1], [4, 5, 1], [4, 6, 5], [5, 6, 7], [0, 2, 4], [2, 6, 4],
+         [3, 7, 6], [2, 3, 6]]
+mesh = trimesh.Trimesh(vertices=vertices, faces=faces)
+normal_plane = [0, 0, 1]
+point_plane = [0, 0, 0.5]
+normal_plane_opp = [0, 0, -1]
+
+# Step 1: division and extraction of segments
+mesh_1 = inter.slice_mesh_plane(mesh, normal_plane, point_plane)
+mesh_1_segments = inter.mesh_plane(mesh, normal_plane, point_plane)
+
+# Step 2: create mesh from point cloud
+points = extract_points(mesh_1_segments)
+normals = np.empty((len(points), 3))
+for i in range(0, len(normals)):
+  normals[i] = normal_plane_opp
+mesh_2 = point_cloud_to_mesh(points, normals)
+
+# Step 3: merge both meshes
+mesh_final = merge_meshes(mesh_1, mesh_2)
+
+
+print(mesh_final.vertices, mesh_final.faces)