void AddPendingClusterIndexOperation ( [FClusterUnionIndex](API\Runtime\Chaos\Chaos\FClusterUnionIndex) Index, [EClusterUnionOperation](API\Runtime\Chaos\Chaos\Chaos__EClusterUnionOperation) Op, const [TArray](API\Runtime\Core\Containers\TArray)< [FPBDRigidParticleHandle](API\Runtime\Chaos\Chaos\FPBDRigidParticleHandle) * > & Particles )