ODE and Quake 3 BSP's

[constchar*]

I've written two Quake 3 BSP renderers myself before in two languages,
C# and C++, but now I decided I wanted to write a new one or use Irrlicht
but this time rather then implement the simple collision detection algorithm
found at GameDev.Net, I want to implement a physics engine to handle my
collisions and dynamics but I've got the problem of turning the BSP into a
trimesh.

I initially thought the obvious of just sending the map's triangles as trimesh
to the engine but that seems awefully inefficient when we could use the brushes'
clipping plane insted but I've no clue as to where to begin to convert a series
of planes into a collection of triangles.
Examples seem rather hard to find so I looked into some code for converting
WorldCraft *.map brushes into triangles but all I've found so far is very
cryptic code that's not very self-explanitory.

Could someone with insight help me on this?
Thanks!

[rogerborg]

Irrlicht has a built-in method to create an oct-tree of collision triangles (ISceneManager::createOctTreeTriangleSelector()). Have you had a look at what that produces? Is it of any use?