In response to a query on the Softimage mailing list, here's a very rough proof of concept of two-way coupling between the Lagoa multiphysics solver and Bullet RBD in Softimage.

The workflow is as follows:
- Setup simple Lagoa emitter
- Instance interesting geometry into an ICE pointcloud and add to bullet RBD simulation.
- Clone the Lagoa particles into the RBD pointcloud as RBD bodies in a "just in time" fashion. i.e. they are added to the sim just before the simulation step and deleted just after it. This allows Bullet to be influenced by motion of Lagoa particles.
- To send collision data back to Lagoa, use ICE topology to construct geometry matching the instanced particles. Pipe this mesh (with Lagoa collision attributes) back into the Lagoa simulation.
- This will probably result in a dependency cycle warning, so enable "Disable cycle checking when editing ICE trees. No problemo!

This sim has just a few thousand liquid particles, but should work fine with heavier setups (but who has the time!?)

Here's the Softimage 2013 scene file:

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