At [NvFlex.h:692](https://github.com/NVIDIAGameWorks/FleX/blob/b1ea0f87b72582649c935d53fd8531b1e7335160/include/NvFlex.h#L692), a note says: > A particle should not belong to more than one rigid body at a time. But this isn't actually true. Rigid clusters appear to enforce shape-matching constraints, and it is often the case that it is useful for particles to participate in several such constraints (see, e.g., flexExtSoft.cpp's NvFlexExtCreateSoftFromMesh which adds each particles to, potentially, 2-3 clusters, if I understand correctly). I suggest that this note be removed and the documentation be improved to indicate that `SetRigid` establishes a shape matching constraint, and that particles may belong to several constraints at once.