Use the Particle Continuity node to specify that particles should cross a pair boundary as if it were invisible. Pair boundaries appear when the geometry sequence ends in Form Assembly instead of Form Union. Such boundaries require special handling because the mesh elements on either side of the pair boundary aren’t required to match up exactly.

Select one or more identity pairs to allow particles to cross between the source and destination boundaries of these pairs. Such identity pairs are typically created automatically on interior boundaries when the geometry sequence ends in a Form Assembly node instead of a Form Union node.