When you initialize your game world, you want to fill the empty scene. Maybe you add a ground with streets and some buildings, or a terrain with forests and caves. You strategically place your players and enemies, and you sprinkle some treasure and traps on the map. Now how exactly do you tell the jMonkeyEngine where to place an object? You need a way to orient yourself in 3D space—through a coordinate system.
The following figure is based on an image created by Sakurambo, and can be found at http://de.wikipedia.org/w/index.php?title=Datei:3D_coordinate_system.svg.
The jMonkeyEngine uses a right-handed coordinate system, just as the Open Graphics Library (OpenGL) does.
Tip
If the concept of coordinates is new to you, you may want to start with a quick visual introduction on our web page, which can be found at:
http://jmonkeyengine.org/wiki/doku.php/jme3:scenegraph_for_dummies
Let's have a look at the illustration and recapitulate the concepts behind the Cartesian...