In this paper we present a rigorous vector 3D lithography simulator METROPOLE-3D which is designed to run moderately fast on conventional engineering workstations. METROPOLE-3D solves Maxwell's equations rigorously in three dimensions to model how the non-vertically incident light is scattered and transmitted in non-planar structures. METROPOLE-3D consists of several simulation modules: photomask simulator, exposure simulator, post-exposure baking module and 3D development module. This simulator has been applied to a wide range of pressing engineering problems encountered in state-of-the-art VLSI fabrication processes, such as layout printability/manufacturability analysis including reflective notching problems and optimization of an anti-reflective coating (ARC) layer. Finally, a 3D contamination to defect transformation study was successfully performed using our rigorous simulator.