Greetings, I am testing the SixDofSpringJoint class (docs: https://javadoc.jmonkeyengine.org/v3.x/com/jme3/bullet/joints/SixDofSpringJoint.html#enableSpring-int-boolean- , source code: https://github.com/jMonkeyEngine/jmonkeyengine/blob/master/jme3-bullet/src/main/java/com/jme3/bullet/joints/SixDofSpringJoint.java) for a future project that I already mentioned earlier in other article (Gravitation Simulator 2 is released! (public domain) and Universor Project is being worked). I want to connect two cubes with a SixDofSpringJoint but they donâ€™t come together. When I put an index on enableSpring(â€¦) between 0 and 3, the cubes disappear. If I make it bigger, the cubes donâ€™t come together. What am I doing wrong?

```
// Box 1
Box b1 = new Box(0.5f, 0.5f, 0.5f);
Geometry geom1 = new Geometry("Box 1", b1);
Material mat = new Material(assetManager, "Common/MatDefs/Misc/Unshaded.j3md");
mat.setColor("Color", ColorRGBA.Gray);
geom1.setMaterial(mat);
rootNode.attachChild(geom1);
RigidBodyControl rbc1 = new RigidBodyControl(3);
geom1.addControl(rbc1);
bulletAppState.getPhysicsSpace().add(rbc1);
rbc1.setGravity(ZERO);
// Box 2
Box b2 = new Box(0.5f, 0.5f, 0.5f);
Geometry geom2 = new Geometry("Box 2", b2);
geom2.setMaterial(mat);
rootNode.attachChild(geom2);
geom2.setLocalTranslation(Vector3f.UNIT_X.mult(2));
RigidBodyControl rbc2 = new RigidBodyControl(3);
geom2.addControl(rbc2);
bulletAppState.getPhysicsSpace().add(rbc2);
rbc2.setGravity(ZERO);
rbc2.setLinearVelocity(Vector3f.UNIT_X.mult(2));
// Joint
SixDofSpringJoint joint = new SixDofSpringJoint(rbc1, rbc2, Vector3f.UNIT_X, Vector3f.UNIT_X.mult(-1), rot1, rot2, true);
joint.enableSpring(4, true);
bulletAppState.getPhysicsSpace().add(joint);
```

Since I didnâ€™t know much about the usefulness of the matrices that are passed as a parameter in SixDofSpringJoint, I tried to put all the elements of the rot1 and rot2 matrices with ones. I changed them to 0 or 0.2f but nothing changes.