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Question Coordinate system and placement for Boolean Solids  

Forum: Geometry
Date: 08 Apr, 2014
From: Anthony Villano <Anthony Villano>

Hi,

In all references for Geant4 geometry building that I could find on the web (the manuals seem to explain only the absolute simplest case which is not useful for me), I have learned that boolean solids inherit the coordinate system of the "first" solid used in the operation. For example, if I understand, in the following code:

G4VSolid* returnBox = new G4SubtractionSolid(name,solidBox,enclBox,rm,shift);

or

G4VSolid* returnBox = new G4UnionSolid(name,solidBox,roofSlice,rm,shift);

Each of the resulting solids should have the coordinate system defined by the "solidBox."

This appears NOT to be the case when I try to place the figures. After making them into logical volumes and then placing them in the mother with the code:

physicalAirBox = new G4PVPlacement(0,
                        positionAirBox,
                        "AirBox_P",
                        logicalAirBox,
                        //physicalVacBox,
                        physicalWorld,
                        false,
                        0);

Where "logicalAirBox" is the logical volume made from one of the above solids "returnBox" and "physicalWorld" is the physical volume corresponding to the whole world volume. I do not have a good understanding of what the G4PVPlacement argument corresponding to "boolean operation" does, I have it set to false but setting it to true does not change the behaviour.

Can anyone comment on what might be wrong here? I can come up with a concrete and small example, but that will take some time so won't do it unless I have to. The problem is that when I look in the G4 geometry viewer and set to look along the symmetry axis of my shape, panned to align the center of the world with (what I thought should be) the origin of my volume, the volume is shifted off-center.

I am using Geant4.9.3.p02 -- I am in the process of upgrading the simulation to a more modern version but need to fix some geometry issues first.

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1 Feedback: Re: Coordinate system and placement for Boolean Solids   (Michael H. Kelsey - 10 Apr, 2014)
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