Topology optimization is very much necessary to generate feasible designs from basic design maintaining the functionalities. The efficient designs and 2D/3D drawings with several candidate solutions is becoming necessary in several viewpoints. A multi-component topology optimization method for structural assemblies that are made of components produced by die casting processes, where each part is guaranteed to be free from fully enclosed cavities and undercuts in the direction of die drawing are discussed. Moreover, 3D reconstruction of an indoor scene with large vertical span have been described. It represents a novel approach for 3D reconstruction of indoor scenes. It employed the 3D visual reconstruction model of indoor scene by the top-down image registration of point cloud data. The chapter also discussed a detailed optimization process of the combination of VR and VR-GIS. Moreover, two machine learning-based heuristic approaches to constructing sparse flexible designs that leverage a neural network to accurately and quickly predict the performance of large numbers of candidate designs.