> restart;

> r:=cos(t);

> x:=r*cos(s);

> y:=r*sin(s);

> z:=sin(t);

> a:=plot3d([x,y,z],s=0..Pi/2,t=0..2*Pi,scaling=constrained,color=coral):

> b:=plot3d([x,y,z],s=Pi/2..Pi,t=0..2*Pi,scaling=constrained,color=cyan):

> with(plots):

Warning, the name changecoords has been redefined

> c;

轉成vrml檔

> with(plottools):

> vrml(c,"c:/042/9/9-2.wrl",background_color=white);