> with(plots):with(plottools):

> x:=cos(t):

> y:=sin(t):

> z:=(1-s)*2+s*x:

> a1:=plot3d([x,y,z],t=-Pi/4..Pi/4,s=0..1,scaling=constrained,grid=[20,5]):

> a2:=rotate(a1,0,0,2*Pi/4):

> a3:=rotate(a1,0,0,4*Pi/4):

> a4:=rotate(a1,0,0,6*Pi/4):

> a:=display(a1,a2,a3,a4):

> b1:=reflect(a,[[0,0,0],[1,0,1],[1,1,1]]):

> b2:=rotate(b1,0,0,2*Pi/4):

> c:=display(a,b1,b2):

> d:=reflect(c,[0,0,0]):

> h:=display(c,d):

> h;

> vrml(h,"C:/My Documents/trfa/wrl/11-12.wrl",background_color=white);

>