  Modeling arbitrarily large deformations of surfaces smoothly embedded in
three-dimensional space is challenging. The difficulties come from two aspects:
the existing geometry processing or forward simulation methods penalize the
difference between the current status and the rest configuration to maintain
the initial shape, which will lead to sharp spikes or wiggles for large
deformations; the co-dimensional nature of the problem makes it more
complicated because the deformed surface has to locally satisfy compatibility
conditions on fundamental forms to guarantee a feasible solution exists. To
address these two challenges, we propose a rotation-strain method to modify the
fundamental forms in a compatible way, and model the large deformation of
surface meshes smoothly using plasticity. The user prescribes the positions of
a few vertices, and our method finds a smooth strain and rotation field under
which the surface meets the target positions. We demonstrate several examples
whereby triangle meshes are smoothly deformed to large strains while meeting
user constraints.
