In Chapter 4: Loops, Arrays, Switch, Enumerations, and Functions - Implementing Game Mechanics, we talked about scope. The concept that variables declared in a function or inner block of code only have scope (can be seen or used) in that function or block. Using only the C++ knowledge we have at the moment, this can cause a problem. What do we do if we need to work on a number of complex objects which are needed in main? This could imply that all the code must be in main.

In this chapter we will explore C++references which allow us to work on variables and objects that are otherwise out of scope. In addition, references will help us avoid having to pass large objects between functions, which is a slow process. It is a slow process because each time we do this, a copy of the variable or object must be made.

Armed with this new knowledge about references, we will take a look at the SFML VertexArray class that allows us to build up a...