Better Pipe Render

Improvement of pipe rendering.
Before :
![before](https://f.cloud.github.com/assets/5029128/811429/77e29c7a-eed4-11e2-8578-5954c3c285d3.png)
After:
![after](https://f.cloud.github.com/assets/5029128/811431/82f4c0de-eed4-11e2-9da4-5070435d4d32.png)