Software to display 3D surfaces

WolframAlpha is a free online service that can draw implicit surfaces. It is essentially the same as the program Mathematica, but with limited capabilties (for example, it is not able to plot more than one surface at a time).

This code will plot the unit sphere:

ContourPlot3D[x^2+y^2+z^2==1,{x,-1,1},{y,-1,1},{z,-1,1}]

Here is the output online, and here is a screen capture:

Try these for algebraic surfaces:

• surf generates excellent images.
• surfer
• surfex

from http://www.algebraicsurface.net/.