“Physically Based” always seemed to be a grammatical error to me.

“Physically” is an adverb, which should modify an adjective or verb. So parsing the phrase, “physically based” implies that “based” is used as an adjective or verb, which would imply that “physically based rendering” is a special form of “based rendering”, which makes no sense.

“What kind of rendering is it? Based rendering. What kind of Based rendering? Well, Physically Based, of course.”

It should probably instead be “physics based rendering”, right?

Edit: english.stackexchange seems to agree, although it’s closed as offtopic: https://english.stackexchange.com/questions/165416/is-physic...