@Override
    public void read(JmeImporter importer) throws IOException {
        InputCapsule cap = importer.getCapsule(this);
        x = cap.readFloat("x", 0);
        y = cap.readFloat("y", 0);
        z = cap.readFloat("z", 0);
        w = cap.readFloat("w", 1);
    }
De-serializes from the specified importer, for example when loading from
a J3O file.

@param importer the importer to use (not null)
@throws IOException from the importer
jme3-core/src/main/java/com/jme3/math/Quaternion.java