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Sad For John Allison: how come I get "unknown faces!!" when hollowing out a box? 

Keywords: Boolean Processor error unknown faces G4SubtractionSolid
Forum: Geometry
Date: 12 May, 2005
From: Blair Smith <bmsmith@lsu.edu>

John, I read all the threads on HyperNews concerning G4SubtractionSolid operations failing to get visualized. But I found the same error when subtracting a G4Box from a G4Box with a translation on the subtracted box that leaves a 0.075 cm thin front wall. According to my calculations this should not be a problem because I should end up with a simple hollow box with five walls 2mm thick, and a front wall 0.5mm thick. This should not pose a problem for visualization, yet it does!!

Also, I was able to visualize a hollow box without doing the small translation for the subtracted volume. So it's the extra wee translation that is problematic for the BooleanProcessor. Yet, I'm fairly certain my box dimensions are good so that I'm not coinciding any surfaces.

Surely that thickness is large enough that surfaces are not getting lost, and are not being fooled into being coincident? How can my 0.075cm gap be concidered as yielding coincident surfaces with my boaxes (seee code list below)? I say it cannot! But apparently the geometry visualization still gets stuffed up. (Using geant4.7.0.p01)

Below is my code, where I have,

houseLength = 10.06*cm; houseWidth = 4.62*cm; houseHeight = 4.62*cm; innerHouseLength = 9.66*cm; innerHouseWidth = 4.22*cm; innerHouseHeight = 4.22*cm; houseThickness = 2.0*mm; houseFrontThickness = 0.5*mm;

---
G4Box* houseOuterWall = new G4Box("HouseOuterWall", 0.5*houseLength, 
                         0.5*houseWidth, 0.5*houseHeight);
    G4Box* houseInnerWall = new G4Box("HouseInnerWall",
			 0.5*innerHouseLength,
			 0.5*innerHouseWidth,
                         0.5*innerHouseHeight);
    G4double innerHouseDeltaX = houseThickness - 0.5*(houseLength - innerHouseLength);
    solidHouse = new G4SubtractionSolid("House",houseOuterWall,houseInnerWall,
					0,
					G4ThreeVector(innerHouseDeltaX,0.,0.)
					);
    logicHouse = new G4LogicalVolume(solidHouse,houseMat,"House",0,0,0);

    G4ThreeVector xpHouse(-0.5*houseLength + insulatorThickness 
			  + houseThickness, 0., 0.);
    physHouse = new G4PVPlacement(0,             // no rotation wrt mother
                                  xpHouse,       // at (x,y,z) wrt mother
                                  logicHouse,    // its logical volume
                                  "House",       // its name
                                  logicWorld,    // its mother volume
                                  false,         // no boolean operations
                                  0);            // no particular field 

---

Can you see what the problem might be?

Thanks,

Blair

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1 None: Re: For John Allison: how come I get "unknown faces!!" when hollowing out a box?   (Blair Smith - 12 May, 2005)
1 None: Re: For John Allison: how come I get "unknown faces!!" when hollowing out a box?   (John Allison - 12 May, 2005)
4 Question: Re: For John Allison: how come I get "unknown faces!!" when hollowing out a box?   (Blair Smith - 12 May, 2005)
1 None: Re: For John Allison: how come I get "unknown faces!!" when hollowing out a box?   (John Allison - 13 May, 2005)
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