Introduction to Bullet:
Bullet is the modern physics engine that the OpenSim development team is heading towards during the version 8.x builds of OpenSim. Although it's only bullet version 3.x it provided a more robust collision detection for regions to make them feel more like the Second Life regions. It is uncertain of Bullet development will continue with the introduction of AviNations code-merge of their updated ODE Physics which allows for better prim sitting and vehicle crossing from region to region. Currently, although you can follow all of the steps and compile bullet onto your Arm-based Pi. Bullet simple does not run and you must run Bulletin XNA mode which isn't optimal.