> restart: with(plots):with(plottools):
> r:=4:  
> x:=(r+cos(v))*cos(u):
> y:=(r+cos(v))*sin(u):
> z:=sin(v)*sqrt((Pi-abs(u))/Pi):
> gsz0:=plot3d([x,y,z],u=-Pi..Pi,v=u/2-Pi/2..u/2+Pi/2,grid=[25,2],scaling=constrained):
> gsz1:=plot3d([x,y,z],u=-Pi..Pi,v=u/2+Pi/2..u/2+3*Pi/2,grid=[25,7],scaling=constrained):
> gsz1b:=plot3d([x,y,sin(v)],u=-Pi..Pi,v=u/2+Pi/2..u/2+3*Pi/2,grid=[25,7],scaling=constrained):
> gsz2b:=plot3d([x,y,sin(v)],u=-Pi..Pi,v=u/2-Pi/2..u/2+Pi/2,grid=[25,7],scaling=constrained):
> 
> gsz2:=plot3d([x,y,z],u=-Pi..Pi,v=u/2-Pi/2..u/2+Pi/2,grid=[25,7],scaling=constrained):
> gsz12:=plot3d([x,y,z],u=-Pi..Pi,v=u/2-Pi/2..u/2+3*Pi/2,grid=[25,13],scaling=constrained):
> v1:=u/2+Pi/2:
> x1:=(r+cos(v1))*cos(u):
> y1:=(r+cos(v1))*sin(u):
> z1:=sin(v1)*sqrt((Pi-abs(u))/Pi):
> # z1:=sin(v1): # a nem lapított változathoz
> vonal1:=tubeplot([x1,y1,z1],u=-Pi..Pi,radius=0.1,
> grid=[25,5],scaling=CONSTRAINED, color=BLACK,  style=PATCHNOGRID):
> v2:=u/2-Pi/2:
> x2:=(r+cos(v2))*cos(u):
> y2:=(r+cos(v2))*sin(u):
> z2:=+sin(v2)*sqrt((Pi-abs(u))/Pi):
> # z2:=sin(v2): # a nem lapított változathoz
> vonal2:=tubeplot([x2,y2,z2],u=-Pi..Pi,radius=0.1,
> grid=[25,5],scaling=CONSTRAINED, color=BLACK,  style=PATCHNOGRID):
> torusz:=tubeplot([r*cos(v),r*sin(v),0],v=0..2*Pi,radius=0.9
> ,grid=[25,13],scaling=CONSTRAINED, color=GREY,  style=patchnogrid):
> display3d(gsz0,vonal1,vonal2,orientation=[150,70]);
> vrml(display3d(gsz0,vonal1,vonal2,color=yellow,style=PATCHNOGRID,orientation=[147,73]),`gsz0v.wrl`,background_color=COLOR(RGB,0,1,1), shininess=0.5, specular_color=COLOR(RGB,1,1,1)):
> gsz0;
> gsz1b;
> gsz1;
> gsz12;