# Computing vorticity and Q-criterion with the "Gradient of Unstructured Data set" filter

Hi. I’m currently trying to calculate the vorticity and the q-criterion using the “Gradient of Unstructured Data set” filter, with the velocity data set of a Cartesian grid, formatted as follows.

density u v w
value value value value
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .
. . . .

I use the calculator filter and use

uiHat+vjHat+w*kHat

to construct my velocity factor, to which I apply the “Gradient of Unstructured Data set” filter.

From my online research, it should show me the “Compute vorticity” and “Compute QCriterion” options, but I do not see those options pop up when I select the filter. I’d appreciate it if you could let me know why I don’t see those options.

Thanks for you time.

Hi Peter, and welcome to the ParaView community!

The Properties tab for filters is so incredibly rich, that we try to only show what is commonly used. What you are looking for is an “advanced” feature. Click on the little gear, on the Properties tab of the Gradient of Unstructured filter. You will then see these options.

@wascott

Walter, thanks so much for the kind answer! Works now

I am facing the same problem where I have a csv file with three cols having velocity magnitude. So I reconstructed the velocity vector using the calculator : U:0iHat+U:1jHat+U:2*kHat

Then I applied “Gradient of Unstructured Data set” filter and calc QCriterion but the results I am getting is wrong. QCriterion ranges from 0 to 3.4e+38 there are no negative values which is weird