JME 3 Tutorial (2) - Hello Node

package jme3test.helloworld;
import com.jme3.app.SimpleApplication;
import com.jme3.material.Material;
import com.jme3.math.Vector3f;
import com.jme3.scene.Geometry;
import com.jme3.scene.shape.Box;
import com.jme3.math.ColorRGBA;
import com.jme3.scene.Node;
/** Przykład 2 - How to use nodes as handles to manipulate objects in the scene graph.
 * You can rotate, translate, and scale objects by manipulating their parent nodes.
 * The Root Node is special: Only what is attached to the Root Node appears in the scene. */
public class HelloNode extends SimpleApplication {
    public static void main(String[] args){
        HelloNode app = new HelloNode();
        app.start();
    }
    @Override
    public void simpleInitApp() {
        // create a blue box at coordinates (1,-1,1)
        Box box1 = new Box( new Vector3f(1,-1,1), 1,1,1);
        Geometry blue = new Geometry("Box", box1);
        Material mat1 = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        mat1.setColor("Color", ColorRGBA.Blue);
        blue.setMaterial(mat1);
        // create a red box straight above the blue one at (1,3,1)
        Box box2 = new Box( new Vector3f(1,3,1), 1,1,1);
        Geometry red = new Geometry("Box", box2);
        Material mat2 = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        mat2.setColor("Color", ColorRGBA.Red);
        red.setMaterial(mat2);
        // create a pivot node at (0,0,0) and attach it to root
        Node pivot = new Node("pivot");
        rootNode.attachChild(pivot);
        // attach the two boxes to the *pivot* node!
        pivot.attachChild(blue);
        pivot.attachChild(red);
        // rotate pivot node: Both boxes have rotated!
        pivot.rotate( 0.4f , 0.4f , 0.0f );
    }
}----
Build and run the code sample. You should see two colored boxes tilted at the same angle.



== Understanding the Terminology

In this tutorial, you will learn some new terms:


.  The _scene graph_ represents your 3D world.
.  Objects in the scene graph (such as the boxes in this example) are called _Spatials_.
**  A Spatial is a collection of information about an object: its location, rotation, and scale.
**  A Spatial can be loaded, transformed, and saved.

.  There are two types of Spatials, _Nodes_ and _Geometries_.
.  To add a Spatial to the scene graph, you attach the Spatial to the _rootNode_.
.  Everything attached to the _rootNode_ is part of the scene graph.


== Understanding the Code

So what exactly happens in this code snippet? Note that we are using the `simpleInitApp()` method that was introduced in the first tutorial.


.  We create a box Geometry.
**  The box Geometry's extends are (1,1,1), that makes it 2x2x2 world units big.
**  We place the box at (1,-1,1)
**  We give it a solid blue material.
[source,java]

        Box box2 = new Box( new Vector3f(1,3,1), 1,1,1);
        Geometry red = new Geometry("Box", box2);
        Material mat2 = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
        mat2.setColor("Color", ColorRGBA.Red);
        red.setMaterial(mat2);----

.  We create a Node.
**  By default the Node is placed at (0,0,0).
**  We attach the Node to the rootNode.
**  An attached Node has no visible appearance in the scene.
[source,java]

        pivot.attachChild(blue);
        pivot.attachChild(red); ----

.  Now, we rotate the node.
**  _When we run the application now, we see two boxes on top of each other – but both are tilted at the same angle._
[source,java]