I have a 2D velocity vector and I would like to visualise the streamlines. As you can see on the attached image, all the filters are greyed out, including the little buttons in the third line. Could someone tell me why all filters are unavailable at this point?

I havenâ€™t look at the data set, but it sounds like the problem is that you have 2D vectors and the streamline filter is expecting 3D vectors. You can fix the problem using the Calculator filter to convert the 2D vector to the 3D vector. Simply set the Expression of the calculator to something like velocity_X*iHat+velocity_Y*jHat (where velocity is replaced with whatever name your 2D velocity field has).

Thank you for your idea. I donâ€™t know what I am doing wrong, but all filters are greyed out (as shown at my first post in this topic). So I can not use the Calculator filter to make the the 2D data into 3D, as the Calculator filter is unavailable as well.