  We introduce a method to design lightweight shell objects that are
structurally robust under the external forces they may experience during use.
Given an input 3D model and a general description of the external forces, our
algorithm generates a structurally-sound minimum weight shell object. Our
approach works by altering the local shell thickness repeatedly based on the
stresses that develop inside the object. A key issue in shell design is that
large thickness values might result in self-intersections on the inner boundary
creating a significant computational challenge during optimization. To address
this, we propose a shape parametrization based on the solution to the Laplace's
equation that guarantees smooth and intersection-free shell boundaries.
Combined with our gradient-free optimization algorithm, our method provides a
practical solution to the structural design of hollow objects with a single
inner cavity. We demonstrate our method on a variety of problems with arbitrary
3D models under complex force configurations and validate its performance with
physical experiments.
