Non-linear rotation values from getWorldRotation()

Troubleshooting SDK
1

Help!
I’m looking for a way to get a rotation value that is linearly proportional to the spatial’s actual rotation (without having to tack on some extra trigonometry every time.) I am new to the SDK so forgive me if I’ve missed something. This code sample should explain it. From the comments:

//Watch the output. Notice that the delta (right column)  which should remain constant,
//does not. It changes sinusoidally from ~.05 to ~0.0 as it reaches the 
//max angular deflection of 1.0/-1.0

Thank you. -Andrew

package mygame;

import com.jme3.app.SimpleApplication;
import com.jme3.input.ChaseCamera;
import com.jme3.material.Material;
import com.jme3.math.;
import com.jme3.renderer.RenderManager;
import com.jme3.scene.;
import com.jme3.scene.shape.Cylinder;

public class Main extends SimpleApplication {

Cylinder c;
Geometry geom;
float temp = 0;
public static void main(String[] args) {
    Main app = new Main();
    app.start();
}

public void simpleInitApp() {
    c = new Cylinder(11,11,1,.1f,5,true,false);
    geom = new Geometry("Cyclinder", c);
    Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
    mat.setColor("Color", ColorRGBA.Blue);
    geom.setMaterial(mat);
    rootNode.attachChild(geom);
    flyCam.setEnabled(false);
    ChaseCamera chaseCam = new ChaseCamera(cam,geom,inputManager);
    chaseCam.setInvertVerticalAxis(true);
}

//Watch the output. Notice that the delta (right column)  which should remain constant,
//does not. It changes sinusoidally from ~.05 to ~0.0 as it reaches the 
//max angular deflection of 1.0/-1.0
public void simpleUpdate(float tpf) {
    geom.rotate(0, .1f, 0);
    try {Thread.sleep(1000);} catch (InterruptedException ex) {}
    float newAngle = geom.getWorldRotation().getY();
    float delta = newAngle-temp;
    System.out.println(newAngle+"\t"+delta);
    temp = newAngle;
}

}

2

You seem to be under the impression that Quaternion values can make some sense or be angles or something. They can’t.

A quaternion is a magic set of values. Unless you can visualize 4 dimensional space then it is unlikely that you will see what they mean… that’s why there are all of these different methods on them for getting angles and stuff. It is important to use those methods instead of the magical values if you really need angles.

However, if you describe why you want the angles perhaps we can show you a better way. Almost always when a user thinks they need angles it’s because they are adding extra unneeded steps somewhere. Not always but at least 90% of the time.

Edit: because the other thing is that those angles will jump around because a Quaternion is not a set of angles. It’s a compact rotation in 3 dimensions.

3

Ahhh. By all these different methods you mean in this case, toAngles(). That’s all I needed. Don’t think I read that one closely enough. Radians work nicely. Thanks for the help.