public Quaternion subtractLocal(Quaternion q) {
        this.x -= q.x;
        this.y -= q.y;
        this.z -= q.z;
        this.w -= q.w;
        return this;
    }
Subtracts the argument and returns the (modified) current instance.

<p>To quantify the similarity of 2 normalized quaternions, use
{@link #dot(com.jme3.math.Quaternion)}.

@param q the quaternion to subtract (not null, unaffected unless it's
    {@code this})
@return the (modified) current instance
jme3-core/src/main/java/com/jme3/math/Quaternion.java