How to Add a Ground Plane?

```
Hi,

I am planning to add a ground plane to the viewer permanently. I use the viewer
mainly to display buildings (stl files), so it would be more realistic to have
the ground. Originally I though I might be able to load multiple stl files on a
scene(ground plane and a building), but one model could be so large that it
completely enclose the other. Can you please give me a hint how I can start the
process? Thank you very much!

Kai L.
```

Original issue reported on code.google.com by `liuwukai...@gmail.com` on 22 Jun 2014 at 2:29

The issue names no files, tests, or entry points. Start by identifying how the viewer builds a scene and loads STL models; clarify the desired permanent ground-plane behavior before implementation, since the report currently asks for guidance rather than defining acceptance criteria.

Written by the indexing model from the issue text.