void TFacet(Int_t nPatches) 
{

  if (nPatches < 1) return;
  Float_t maxD = (Float_t)nPatches;

  TGeoManager *manager = new TGeoManager("world","My World");
  TGeoMaterial *air = new TGeoMaterial("Vacuum",0,0,0);
  TGeoMedium *vacuum = new TGeoMedium("Vacuum",1,air);
  
  TGeoVolume *top = manager->MakeBox("Top",vacuum,maxD,maxD,maxD);
  manager->SetTopVolume(top);

  Float_t dx=1., dy=1., dz=1.;
  Int_t count=0, jcount=0, icount=0;

  for (Int_t i=0; i<nPatches; i++) {
    printf("Level %d\n",i);
    TGeoTranslation *tr_x = new TGeoTranslation(i*dx,0,0);
    TGeoVolume *inode = manager->MakeBox(Form("inode%d",icount++),vacuum,1.,maxD,maxD);
    top->AddNode(inode,icount,tr_x);
    inode->SetVisibility(kFALSE);

    for (Int_t j=0; j<nPatches; j++) {
      TGeoTranslation *tr_y = new TGeoTranslation(0,j*dy,0);
      TGeoVolume *jnode = manager->MakeBox(Form("jnode%d",jcount++),vacuum,.4,.4,maxD);
      inode->AddNode(jnode,jcount,tr_y);
      jnode->SetVisibility(kFALSE);

      for (Int_t k=0; k<nPatches; k++) {
	TGeoTranslation *tr_z = new TGeoTranslation(0,0,k*dz);
	TGeoVolume *box1 = manager->MakeBox(Form("box%d",count++),vacuum,.15,.15,.15);
	box1->SetLineColor(kBlue);
	jnode->AddNode(box1,count,tr_z);

      }
    }
  }
  manager->CloseGeometry();
  manager->SetVisLevel(3);
  

  top->Draw("ogl");

}