Filling Holes in Point Clouds

### Checklist

- [X] I have searched for [similar issues](https://github.com/isl-org/Open3D/issues).
- [X] For Python issues, I have tested with the [latest development wheel](http://www.open3d.org/docs/latest/getting_started.html#development-version-pip).
- [X] I have checked the [release documentation](http://www.open3d.org/docs/release/) and the [latest documentation](http://www.open3d.org/docs/latest/) (for `master` branch).

### My Question

Hello,

I'm trying to fill empty holes in my point cloud. The depth image was captured using a downward-facing camera positioned on the upper section of a truck. Unfortunately, due to the angle of the camera, it was not possible to generate point clouds for the walls of the dump body.

Is it possible to create a wall of point clouds to close the dump body (dotted green lines)? Any ideas of how I could do this with Open3D?


Thanks