Mixing things up

Now that we are rendering in 3D, it isn't immediately obvious how we will render things in 2D. This is especially true of our user interface, which must be rendered on top of the 3D-scene and does not move or rotate with the rest of the world.

The trick to creating a 2D interface in a 3D world is to first render the 3D world, then switch modes in OpenGL, and then render the 2D content. The following image represents the 3D content that we need to render:

The next image represents the 2D text that we want to render:

We want the final result to be the combination of the 3D and 2D content, as shown in the following figure:

The saving state

State is a term that is used in many different ways in game programming. For example, we will create a state manager later in the chapter that will manage different states, or modes, in the game. Another way to define state is a set of conditions. For example, when we set things up to render in 3D, this is one set of conditions or state...