Greater reliability and large computational savings can be achieved by linking the adaptive iteration of a computational analysis with the outer, optimization iteration, so that at each optimization step, the analysis performed is as accurate as it needs to be, and no more. Earlier work in this area involving scattering parameter calculation of 2D waveguide structures is extended to 3D with certain modifications. A more robust error estimator is utilized, and tighter accuracy control is applied to a direct optimization strategy that exploits the ready availability of gradient information