11.2.20 bdTorus



  \begin{texgraph}[name=villarceau,export=eps]
  view(-6,6,-5,5),Marges(0,0,0,0),size(7.5),
  $R:=3, $r:=1,
  N:=rot3d(vecK,[Origin,vecI],arcsin(r/R)),
  view3D(-5,5,-5,5,-5,5),
  background(full,lightgray),
  Build3D(
   bdPlan([Origin, -N],
      [color:=seagreen, opacity:=0.8]),
   bdTorus( Origin, R, r, vecK,
      [color:=steelblue, smooth:=1]),
   view3D(-5.5,5.5,-5.5,5.5,-5,5),
   bdAxes( Origin,
      [arrows:=1, newxlegend("x"),newylegend("y"),
       newzlegend("z")]),
   bdCercle(M(r,0,0),R,N,[color:=red, tube:=1]),
   bdCercle(M(-r,0,0),R,N,[color:=red, tube:=1])
          ),
  Display3D()
  \end{texgraph}

 PIC



villarceau circles