Field arrays filter spatially. On dipping arrivals this produces a temporal filtering effect. To match field arrays, Kirchhoff operators are designed to antialias with short rectangle and triangle smoothing functions whose duration depends on the local trace-to-trace moveout. Integrals under triangular shaped weighting windows are rapidly computed from the double integral of the trace. Each integral is a weighted sum of three values of the double integral, one from each corner of the triangle. Complete code is given along with examples.