PRESENTATION OF BSP PROJECT

Project presentation and organisation:

The "BSP Trees Project" (part I&II) purpose was to create and visualize a 3D model of the ESSI building using BSP Trees methods.

Meanwhile the Part I team (let's call it "Team I") used to deal with BSP utilisation and visualisation problems (click here for their own page), the Part II team ( logically called "Team II") deals more particulary with the modelisation and BSP generation.

During three weeks (ten days of effective work due to administrative and technical problems), we worked on modelisation of the second and third level of ESSI with a Quake level editor: WorldCraft. The underlying idea was to test and evaluate the efficiency of BSP Trees methods on such a complexe model we made, using the Team I program and Quake 3D engine which is actually one of the most efficient ones.

Looking after that goal we had first to learn the basis principles of BSP Trees, an essential preliminary phase in order to build a coherent BSP file (for exemple: NEVER make coplanar walls...WorldCraft doesn't like them at all). Then we entered the modelisation phase where we had to face modelling problems of course (ESSI is a more complicated structure than it seems) but also other subsidiary ones: textures, lights, quake-C programming for interactivity,...

Project continuation

In the last few days (when ESSI modelisation was almost finished) we decided to include in our project some interaction; we tried to give it the interactivity that misses the VRML model made by our predecessors in ESSI3 during the last two years project, using the amazing potential of the Quake engine (and a 3DFX card). We also coded some monsters behavior because we had time to do it and it would have be a pity not to do use Quake functionnalities.

Conclusion: efficiency evaluation

As showed in the demo, BSP Trees allow our model to be visited with fast animation (about 40 images/second with Quake and 20 images/second with the Team I program) and a total liberty of movements (thanks to real 3D).

Considering the number of polygons of the model we can say that those results are more than conclusive, BSP Trees are a very efficient way to deal with static 3D models like buildings because everything is precomputed ! Drawback of this method, compiling only 2 levels of ESSI (less than half the totality) with generation of BSP file, extra light computation and full visibility determination will take more than 1 hour ! A loss of 1 hour time for a 40 images/second fluid animation anytime after is not a so terrible sacrifice.