3D graphing software (free? linux-compatible?)

Hello everyone, I'm a high school student and I'm looking for some software which will allow me to graph lines and surfaces in 3D, and which will also perform some calculations such as finding intersections of lines and/or surfaces. I have been working on a research project which involved graphing lines and finding their intersections: initially i used a program called GeoGebra, which is very simple but works well. However, extending the investigation I would like to find intersections of plains (for a large range of functions; by hand just won't cut it). I'd prefer the software to be free (even better is it's open source) and also preferably linux compatible. However, just general information on good programs out there would be helpful.

I tried gnuplot, but looking through the documentation I can't find any mention of calculating intersections, and I suspect it is not possible. Is this right?

Thanks in advance.

Dan

Re: 3D graphing software (free? linux-compatible?)

For not too complex problems you can also try this: Plot Graphs . It is online although linux compatible...