One more question. I wrote a bunch of unit tests, and was able to change the code to pass most of them. However, I found that if the model being added does not contain, or border on the point (0, 0, 0) then we handle it all incorrectly. My question is, is this a valid test? Or should/must an object touch the origin? Should there be detection/error reporting if an item doesn't, or is that handled elsewhere (in the tools)?
For now I disabled the tests, and pushed the code because it's better than it was.