Hi Erwin.
I'm studying
COLLADA 1.5 specs in reference of physics export format, Chapter 6. Additionally I'm adapting the source code of COLLADA RT for my engine, cleaning dependencies, not using CG and so on, clean Crt! with no support of COLLADA FX, only geom and calc Skinning, Morphing, etc. So the objective is, load and play COLLADA .dae and get the configuration of COLLADA Physics for configure Bullet physics.
Use NVidia PhysX in 3ds max and export to COLLADA is good for me. The best option is obviously to use Bullet in this plug-in and export to .dae or .bullet.
The most common use of Bullet in my games are to use custom meshes. I create btBvhTriangleMeshShape when I need collision map, ramps for rolling games, etc. For example:
- I create visual object, a ramp with some holes
- Then I create collision object with name "ground"
- I create an Actor with LUA script, CreateActor("ActorPhysic", { ..., node = "ground" }
- When actor is initializing I use the object of node for create btBvhTriangleMeshShape
This way is really useful, work fine for me. The best is support all COLLADA features and all bullet possibilities. This is my objective custom collision meshes and triggers with Bullet primitives.
I want to create complex meshes with Bullet directly in 3ds max, create ropes, rigid bodies, attachments. So I suppose the first pass is to support COLLADA to Bullet using PhysX plug-in and the next step change PhysX by Bullet and collaborate with Bullet scene and help you as possible. Your source code of this plug-in is huge!

I don't know if in my free time I will do that quickly or if I have the experience needed to port that.
PhysX plug-in to COLLADA Physic is up to date?
Thanks!