> restart;

> x:=r*cos(t);

> y:=r*sin(t);

> r:=0.02*t;

> a:=plot3d([s*x,s*y,(1-s)],s=0..1,t=0..30,scaling=constrained,grid=[5,200],color=COLOR(RGB,0.3,0.9,0.3)):

> with(plots):

Warning, the name changecoords has been redefined

> display(a);

> with(plottools);

Error, (in vrml) wrong type of arguments

> vrml(a,"c:/My Documents/mei/10.html/10-5.wrl",background_color=white):

>