Photo-Realism

Often one reads:
"The goal of computer graphics is to produce photo-realistic images."

Clarifications.


In common parlance the term "photorealistic" is loosely defined as "an image that resembles a photograph". In Art, for example, there is a movement called "photorealism" (also "hyperrealism"). These paintings incorporate many photographic artefacts such as limited dynamic range, depth of field and strict linear perspective, to achieve a "photographic look". In general, these effects are exagerated. In a sense these paintings are caricatures of photographs. We rarely mistake them for photographs (only perhaps when they are reproduced as photographs in an art book).


In computer graphics "photorealism" is used in a somewhat different context. Technical papers (especially in "rendering") loosely define "photorealism" as the goal of "creating pictures that are undistinguishable from real photographs". Usually these papers use a physical theory such as radiative transfer (or transport theory) to create such pictures. The rationale behind this approach seems to be that since real photographs result from radiance exciting photoreceptors, therefore in CG we should be modelling radiance and the photographic process. Since we are simulating the "real process" photographic identity should follow.


This approach is in no way necessary to produce picture that are undistinguishable from real photographs.


Take any CG generated picture and photograph it. We know have a picture that trivially resembles a photograph. In this sense any CG generated picture is photorealistic. Since the SIGGRAPH proceedings contain photographs any picture in these proceedings is photorealistic. What went wrong ?


There seems to be consensus amongst CG researchers that "photo-realism" is intimately related to solving integro-differential equations. Do we have to evaluate such research based on imagery or on numerical experiments ? How are the two related ? Are they related ?


CG photorealistic research produces imagery, just like artists produce photorealistic pictures. What is the fundamental difference between the two ?