\enabletrackers[nodes.vsnapping]

\starttext % see spac-ver.mkiv: \definegridsnapping

    \switchtobodyfont[42pt] \setupinterlinespace[line=30pt]

    Big text\par written in\par three row

    \setuplayout[grid=strict] \setupinterlinespace[line=30pt]

    Big text\par written in\par three row

\stoptext

