Remove border from environment model

remove border region from the planar model
* before ![screenshot_from_2014-07-19 17 13 02](https://cloud.githubusercontent.com/assets/40454/3634218/dfd34fbe-0f1c-11e4-8a59-657aae8037dd.png)
* after
![screenshot_from_2014-07-19 17 14 33](https://cloud.githubusercontent.com/assets/40454/3634219/e12ac2e8-0f1c-11e4-9275-f71e4d39030f.png)