Construct this surface:

> restart:

> with(plots):

Warning, the name changecoords has been redefined

> with(plottools):

> r:=exp(-t):

> x:=r*cos(s):

> y:=r*sin(s):

> z:=t+0.03*s:

> a:=plot3d([x,y,z],s=0..8*Pi,t=1..3,scaling=constrained,grid=[100,20]):

> vrml(a,"c:/87138/ex10/10-6.wrl",background_color=white):

> display(a);

>