Graphing a 3D surface with a webtool


SoSH Member
Jul 15, 2005
Milford, CT
Not sure if this belongs in TBLTS but here goes. 
I am trying to make a simple 3D surface as a mockup for a presentation next week and I am having a hard time creating it. This used to be second nature for me when I was in school but I am out of practice and also don't know where the good mathy web-tools are hiding these days. 
The equation is a basic cubic: y=ax^3+bx^2+cx+d. The third variable would be parametric, as an approximation of all the coefficients a-d. For the purpose of the mockup the actual values of the coefficients don't matter, they basically would represent "noise". 
The way I am imaging it is the coefficient parameterization variable would give "depth" to the chart, with the perfect parabola (a=1, b=1, c=1, d=0) in the front. 
Anyways, can anyone point me in the direction of the best freeware to express the above, and possibly a way to set up the graph?