3D graph plot of a function of multiple variables.

[Adel Makram]

I am searching for a site that enables me to plot a function of multiple variables in 3D form. Say f(x1,x2,x3,x4) and I wish to plot this function as a 3D graph for x1 and x2 where x3 and x4 are kept constant.

 

[S.G. Janssens]

I don't know about a site, but is Octave an alternative? It's free in both senses.

 

[gsal]

Python / matplotlib, heck even excel can do that.