Photography by certified artists (or people who can pass themselves off as such) is 100% legal. Examples
"Evidence of Things Unseen" by Simen Johan
"Dressup: Playacts and fantasies of childhood" by Starr Ockenga
"The Boy: A Photographic Essay" by Georges St. Martin
"Boys Will Be Boys" by Georges St. Martin
"In Search of Young Beauty: A Venture Into Photographic art" by Charles Du Bois Hodges
Other than artistic illustrated books, you also have nudist magazines which are also legal. As for drawings, 3DPD and written literature, that is legal so long as it is non-obscene. So in other words, it's hard to really determine what would classify as such and it falls into a legal grey area category, making it borderline illegal. As for photoshopping children's heads onto that of adults in sexual situations, that too is also illegal.
So to any American pedos who want to know their CP law, there you go.