How can I visualize the 3D results from Femlab in Octave / Gnuplot?

I have some data from model in Femlab. Because I would like to work on the results more, I would like to use Octave / Gnuplot as well to visualize the computed data. I have exported the data from Femlab into a txt file in form "x y 开发者_开发百科z value" (4 columns). Everything unsorted - than can I do. But how to get this into gnuplot? I can choose one of the variables to fix it(let's be it x) and plot the rest y,z and value by splot. But, I have thousand and thousand of numbers and this is not possible, than Femlab doesn't keep the variables fixed (so you sort it along x and find out that there are no two x values the same). I know about Femlab / Matlab interface, but unfortunately I havent Matlab. Thank you in advance!

Have you tried scilab? It is a matlab clone like octave and seems to support some FEM stuff: http://wiki.scilab.org/Finite%20Elements%20in%20Scilab.

See also http://www.utc.fr/lrm/giens05/CDROM/CDROM/lo01.pdf a paper where they interface Scilab and OpenFEM.