For example, i might have an environment that is a game level, and my character walks around it. But when i open his inventory it shows another, small environment where i can rotate a character's model, change his equipment and so on. What is the "time-tested" way to do that ? Do i just put all environments i might call on in every game level ? That seems excessive, but i cant think of anything else.
For instance, in Unity i could create a game level in one file, and inventory screen in another, and switch between the two, but it is somewhat problematic to keep track of the data, not to mention there will be a loading time, however small it might be. In most modern games inventory screens and such just come right up, as soon as i press the button. Do people really just put everything in one level ? Please explain this to me.