BulletMultiThreaded/NarrowPhaseCollision makes use of this boxBoxDistance.
Cache some values in src/BulletMultiThreaded/SpuContactManifoldCollisionAlgorithm.cpp, to avoid DMA transfers
2) Added btConvexSeparatingDistanceUtil: this allows caching of separating distance/vector as early-out to avoid convex-convex collision detection.
btConvexSeparatingDistanceUtil is used in src/BulletCollision/CollisionDispatch/btConvexConvexAlgorithm.cpp and can be controlled by btDispatcherInfo.m_useConvexConservativeDistanceUtil/m_convexConservativeDistanceThreshold
3) Use BulletMultiThreaded/vectormath/scalar/cpp/vectormath/scalar/cpp/vectormath_aos.h as fallback for non-PlayStation 3 Cell SPU/PPU platforms (used by boxBoxDistance).
Note there are other implementations in Extras/vectormath folder, that are potentially faster for IBM Cell SDK 3.0 SPU (libspe2)
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