If I want to create a game in which I use sources from another game that has copyright is illegal. But what if I use screenshots from a 3D game to make another 2D game (something like a questionnaire)? Or what if I use the 3D models from the first game, render them with a program like cinema4D or blender in 2D and use them in the 2D game? And if it is illegal please explain me why and what laws of copyright would apply in that case.
I know that observing how a game works or any software for that matter and then reverse engineering it is legal so doing the same thing with resources from a game is legal. That's why I wanted to make clear my question is not related to reverse engineering.