We present a theoretical model for the effect of material pixellation on the operating characteristics of optical logic elements using nonlinear interference filters. From our calculations we predict pixel packing densities of 250×250 per cm2(an increase of three orders of magnitude over optical pixellation) and power levels of 100 &mgr;W. We define a figure of merit which describes the effects of pixellation of thermo‐optic logic elements. We also show numerically the effect on cooling rate.