This is a demo I made in Unity3d for a purpose of the testing of fluid flow in human organs.
A simple tool for creating the geometry was needed. The demo tool I came up with is capable of saving the files in the common 3d formats like .obj or .dae and also outputting it in the special format requred by the simulation program. The image below links to the webplayer which enables you to create, read and edit the branched tubework geometry. The demo operates on files stored on the server.