Set <code>this</code> matrix to its own normal matrix.
<p>
The normal matrix of <code>m</code> is the transpose of the inverse of <code>m</code>.
<p>
Please note that, if <code>this</code> is an orthogonal matrix or a matrix whose columns are orthogonal vectors,
then this method <i>need not</i> be invoked, since in that case <code>this</code> itself is its normal matrix.
In this case, use {@link #set(Matrix3d)} to set a given Matrix3f to this matrix.
Set <code>this</code> matrix to its own normal matrix. <p> The normal matrix of <code>m</code> is the transpose of the inverse of <code>m</code>. <p> Please note that, if <code>this</code> is an orthogonal matrix or a matrix whose columns are orthogonal vectors, then this method <i>need not</i> be invoked, since in that case <code>this</code> itself is its normal matrix. In this case, use {@link #set(Matrix3d)} to set a given Matrix3f to this matrix.
@see #set(Matrix3d)
@return this