生成Octree对象的体素网格。
open3d.geometry.VoxelGrid.create_from_octree(
octree: open3d.geometry.Octree,
voxel_size: float
) -> open3d.geometry.VoxelGrid
参数：
octree: open3d.geometry.Octree类型，用于生成体素网格的octree对象。voxel_size: float类型，体素的大小。返回值：
open3d.geometry.VoxelGrid类型，生成的体素网格对象。说明：
create_from_octree方法将通过一个给定的octree对象生成一个体素网格。
voxel_size参数表示生成的体素的大小。示例：
import open3d as o3d
# 创建Octree对象
octree = o3d.geometry.Octree(max_depth=4)
points = o3d.utility.Vector3dVector([
[0,0,0], [1,0,0], [0,1,0], [1,1,0],
[0,0,1], [1,0,1], [0,1,1], [1,1,1]
])
octree.convert_from_point_cloud(points)
# 生成体素网格对象
voxel_size = 0.1
voxel_grid = o3d.geometry.VoxelGrid.create_from_octree(octree, voxel_size)