Computer graphics has developed practical methods for the description of scenes and their interactions with light. Appearance synthesis is concerned with algorithmic, automated methods for the production of real-world items which look as close as possible to the specified models.
Passive Reflectance Field Displays
One possible solution for appearance synthesis is the concept of a passive reflectance field display: optical constructions which embody a coded reflectance field so that the illumination falling on the display creates an image there, as if another scene was rendered in this illumination [Fuchs et al., SIGGRAPH 2008]. Simple variations of this technique consist of inexpensive components (see fig. 1) and may be assembled with off-the-shelf office equipment. More complex constructions comprise hundreds of optical lenses in precise alignment. In either case, the appearance can be modified by exchanging a pattern printed on a transparency sheet inside the display without modifying the design of the optical components around it. Thus, the appearance of a real-world item may be programmed.
Reflectance fields decouple the looks of a physical artifact from its actual geometry. While this enables self-rendering pictures, this separation of shape and appearance is not always desirable. The method by Hašan et al. [SIGGRAPH 2010] therefore proposes a solution, which stacks different types of plastics with a 3D printing process so that they approximate the appearance of other materials. The techniques focuses on materials such as marble, which transport light below the surface.