3D parametric surface : plotparam paramplot DrawParm

plotparam takes two main arguments, a list of three expressions of two variables and the list of these variable names where each variable name may be replaced by variable=interval to specify the range of the parameters. It accepts an optionnal argument to specify the discretisation steps of the parameters u and v with ustep=... and vstep=....
plotparam([f(u,v),g(u,v),h(u,v)],[u,v]) draws the surface defined by the first argument : x = f (u, v), y = g(u, v), z = h(u, v), where u and v ranges default to the graphic configuration.
Input :

plotparam([v*cos(u),v*sin(u),v],[u,v])

Output :

The cone x = v*cos(u), y = v*sin(u), z = v

To specify the range of each parameters, replace each variable by an equation variable=range, like this:

plotparam([v*cos(u),v*sin(u),v],[u=0..pi,v=0..3])

Output :

A portion of the cone x = v*cos(u), y = v*sin(u), z = v

Input :

plotparam([v*cos(u),v*sin(u),v],[u=0..pi,v=0..3],ustep=0.5,vstep=0.5)

Output :

A portion of the cone x = v*cos(u), y = v*sin(u), z = v