Hollow topology generation with lattices for computer aided design and manufacturing

Methods, systems, and apparatus, including medium-encoded computer program products, for computer aided design of physical structures using generative design processes, where three dimensional (3D) models of the physical structures are produced to include lattices and hollows, include: obtaining design criteria for an object; iteratively modifying 3D topology and shape(s) for the object using a generative design process that represents the 3D topology as one or more boundaries between solid(s) and void(s), in combination with physical simulation(s) with a hollow structure and a lattice representation; adjusting a thickness of the hollow structure; adjusting lattice thickness or density; and providing a 3D model of the generative design for the object for use in manufacturing a physical structure corresponding to the object using one or more computer-controlled manufacturing systems. The providing can include generating instructions for manufacturing machine(s), which can employ various manufacturing systems and techniques, including additive, subtractive and casting manufacturing methods.