Just to let you know the solution of the riddle...I was using log scale...and of course the log scale can't use negative numbers... So, with linear scale and local values of the variables it works perfectly. Sorry about this stupid problem.

Hi J,

Thanks for the update. Don't feel stupid; we've all been there. It never occurred to me to ask whether it was linear or log (most users don't realize they can plot on a log scale).

So I have to ask, were you also plotting on a log scale in Tecplot?

-CycLone

Hi man! Nope, on tecplot I used a normal linear scale. But I want to check also the log scale...and see what Tecplot says to me...

I'd be interested in what Tecplot does. The problem with the log plot is you can never get to zero in order to cross over from negative to positive. One solution would be to have a lower limit on the log scale, after which it switches from positive to negative.

You can emulate this in Post by creating a contour with two levels, one below zero and one above, creating user surfaces on each level, then creating a logarithmic contour on each side with inverted color ranges.

-CycLone