Often in 3D games you want to change how you look at the world. For example, in a first person shooter you probably want to have the camera look from a position a bit above the xy-plane along the xy-plane,
which, in graphics terms, involves setting the correct projection. This projection should be set in an instance that is created before all other instances (you can set this from the Instance Order
window in the Room Editor), and it should be at a very low depth so that is drawn before all other instances in your room, otherwise you will get issues when drawing.
To change the way you look at the 3D world the following functions exist: