Understand Shadowing by pointcloud artifacts on the whole Point Cloud.

### 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 `main` branch).

### My Question

Hello All.

First of all, Thank you so much for the amazing library.

I would like to understand the shadowing of objects on the point cloud. For eg. If I have a person on a point cloud, I would like to understand how the person cast shadows and which points are hidden by the person pcd because of shadowing. I would also like to visualize the ray and shadowing part. I understood a bit on Raycasting Algorithm but I am confused on implementing this with open3d library. If anyone have any suggestions or direction than it would be great.

Thank you.

Regards,
Bishal