  We present a technique to optimize the reflectivity of a surface while
preserving its overall shape. The naive optimization of the mesh vertices using
the gradients of reflectivity simulations results in undesirable distortion. In
contrast, our robust formulation optimizes the surface normal as an independent
variable that bridges the reflectivity term with differential rendering, and
the regularization term with as-rigid-as-possible elastic energy. We further
adaptively subdivide the input mesh to improve the convergence. Consequently,
our method can minimize the retroreflectivity of a wide range of input shapes,
resulting in sharply creased shapes ubiquitous among stealth aircraft and
Sci-Fi vehicles. Furthermore, by changing the reward for the direction of the
outgoing light directions, our method can be applied to other reflectivity
design tasks, such as the optimization of architectural walls to concentrate
light in a specific region. We have tested the proposed method using
light-transport simulations and real-world 3D-printed objects.
