if ( isReverse ) swap ( f, l );
const int nbCol = 5;
for ( int i = 0; i < nbCol; ++i )
{
double u = f + i/double(nbCol) * ( l - f );
if ( isReverse ) swap ( f, l );
const int nbCol = 5;
for ( int i = 0; i < nbCol; ++i )
{
double u = f + i/double(nbCol) * ( l - f );