public Vector3f getColumn(int i) {
        return getColumn(i, null);
    }
Returns the specified column. The matrix is unaffected.

<p>If the matrix is a pure rotation, each column contains one of the
basis vectors.

@param i the column index (0, 1, or 2)
@return a new Vector3f
@throws IllegalArgumentException if {@code i} isn't 0, 1, or 2
@see Quaternion#getRotationColumn(int)
jme3-core/src/main/java/com/jme3/math/Matrix3f.java