I'm pretty new in developing videogames. By now I only used SDL with C/C++ to create games. I'm currently learning OpenGL and I realized that to be fluid and easy to maintain the code must be logically separated. Since I want to use OpenGLES on iOS and Android I was wondering how the engine must be imagined in a technical way, some questions came up: Do I have to separate input/update functions from draw functions in different threads? Is there only one proper way to think a game engine/loop? What kind of assets should I use to create a 3D game using openGl ES to get better performance?