Problem using G4MultiUnion

Geometry, Fields and Transportation
1

Hi,
I’m trying to build a mesh to put it in front of a target. Looking at the forum I found a very useful instrument G4MultiUnion. I built an object done by circle and then I subtracted it from a cylinder, to obtain the mesh. In the following the code:

    auto meshTemplate
    = new G4Tubs("meshTemplate",     // its name
               0, meshRadius, meshThickness/2., 0.0*deg, 360.0*deg); // its size
    
  G4MultiUnion* munion_solid = new G4MultiUnion("UnitedBoxes");
    
  G4int nHole = (G4int) 2*CLHEP::pi*(meshRadius-holeRadius)/(2*holeRadius)-1;//10
    
  G4cout << "Number of holes " << nHole << G4endl;
    
        
  for (G4int i = 0; i < nHole; i++) {
     G4Tubs *holeTemplate
      = new G4Tubs("holeTemplate",     // its name
                    0, holeRadius, meshThickness/2., 0.0*deg, 360.0*deg); // its size
     G4ThreeVector pos = G4ThreeVector((meshRadius-holeRadius)*cos(i*2*CLHEP::pi/nHole), (meshRadius-holeRadius)*sin(i*2*CLHEP::pi/nHole), 0);
     G4RotationMatrix rot = G4RotationMatrix(0, 0, 0);
     G4Transform3D tr = G4Transform3D(rot, pos);
     munion_solid -> AddNode( *holeTemplate, tr );
  }

  munion_solid -> Voxelize();

  G4SubtractionSolid *meshS = new G4SubtractionSolid("mesh", meshTemplate, munion_solid);//munion_solid);

  auto meshLV
    = new G4LogicalVolume(
                 meshS,        // its solid
                 meshMaterial, // its material
                 "mesh");        // its name
    
  new G4PVPlacement(
                0,                // no rotation
                G4ThreeVector(0, 0, 0),  // at (0,0,0)
                meshLV,          // its logical volume
                "mesh",    // its name
                worldLV,          // its mother  volume
                false,            // no boolean operation
                0,                // copy number
                fCheckOverlaps);  // checking overlaps

But when I run the simulation what I find is:

image
image1636×1206 209 KB

The circles, which constitute the mesh’s holes are in the right place, but now the base of the mesh that should be continuous it’s a cloud of points.

Do you have an idea of about it is happening?

2

Yes. As it says (you have to read the message), the polyhedron (the usual way of getting a drawing) has failed for some reason so it is drawing the solid as a cloud of points.

The solid itself may be perfectly OK for tracking - it’s probably just the visualisation that’s having trouble making something it can draw from such complicated solid.

3

Thank you for the reply, my concern was about if the effect is only on visualization or on tracking too.