# Libgdx, how do i get the translation and rotation of a node from a model instance?

I have a model instance of a character, and a model instance of a sword weapon. THe character has a node on his right hand so he can "carry" the sword. Right now I use this code so the sword's transform follows that of the node.

weaponModelInstance.transform.set(modelInstance.transform).mul(weaponAttachmentNode.globalTransform);
weaponModelInstance.transform.rotate(Vector3.Z, -90); // adjustment for blender coordinates
world.modelBatch.render(weaponModelInstance, world.environment);


this works, except that the model instance gets scaled to the scale of the node, which i do not want, i want the weapon to keep its scale. I've tried doing the following code to fix this but I end up getting weird (and wrong) rotations for the sword

weaponModelInstance.transform.set(modelInstance.transform).mul(weaponAttachmentNode.globalTransform);
weaponModelInstance.transform.set(
weaponModelInstance.transform.getTranslation(new Vector3()),
weaponModelInstance.transform.getRotation(new Quaternion()),
new Vector3(1, 1, 1)
);
weaponModelInstance.transform.rotate(Vector3.Z, -90);
world.modelBatch.render(weaponModelInstance, world.environment);


do anyone know how to properly copy the world translation and rotation from the node, but not its scale?

You will need to normalize the rotation matrix to remove its scale.

This can be done by normalizing all 3 rows of the transform basis matrix.

new btMatrix3x3(
transform.getBasis().getRow(0).normalize()
, transform.getBasis().getRow(1).normalize()
, transform.getBasis().getRow(2).normalize()
);


or

new btMatrix3x3(
transform.getBasis()[0].normalize()
, transform.getBasis()[1].normalize()
, transform.getBasis()[2].normalize()
);


This new matrix contains only the rotation without scaling.

If you want to extract the scaling instead:

new btVector3(
transform.getBasis()[0].length()
, transform.getBasis()[1].length()
, transform.getBasis()[2].length()
);

• Alternatively, you could use libgdx's Matrix4#getRotation(Quaternion, boolean), the boolean argument being a "normalizeRotation" flag that, when set to true, tells libgdx to perform this operation for you. – Chris Bode May 2 '15 at 21:11