Problems on point cloud normals

[liushuishui7]

I notice that the point cloud in the example has its own normals, such as bunny.ply,spot.ply,scannet.ply.
How are these normals generated?
There is no sensor location in my own data.
I tried to use open3d's normal estimation, but it was quite different from the example.

[StarsTesla]

You could just estimate with other tools such as open3d