Visualizing invisibility: metamaterials-based optical devices in natural environments.

Photorealistic ray tracing methods have been developed that allow us to see how devices such as imperfect invisible spheres and invisibility cloaks would appear if actually constructed and placed in outdoor environments. The methods developed allow photorealistic depiction of devices with gradient indices of refraction and birefringence or trirefringence in non-Cartesian coordinate systems (and hence accurately handle ray splitting/beam walkoff). The resulting images, which can be rendered in real time to produce animations as will be shown, allow subjective assessment of the performance of optical instruments such as invisibility devices in environments in which they are intended to ultimately be used.