[Gate-users] Brothers volumes at the same position what's occuring

[David Sarrut]

Hello,

In G4 (thus in gate), you could *not* have overlapping volumes. If some
volumes overlap, the result is undefined. To my knowledge, you don't have
the choice, you need to change your geometry.

There is a feature in G4 to deal with overlapping volumes (called parallel
world), but it is not available through gate.

Sincerely,
David

Le jeudi 27 février 2014, MELISSAS Maximilien (SAFRAN) <
maximilien.melissas-alten at safran.fr> a écrit :

>  Dear Gaters,
>
> A question related to my question from yesterday,
> When 2 brothers volume are crossing, what's happening at the crossingpoint.
> Here is a quick example of what I mean, with a mother box having2 daughtersvolume Castor and Pollux
>  /gate/motherbox/daughters/name Castor
> /gate/motherbox/daughters/insert cylinder
> /gate/Castor/geometry/setHeight 20. mm
> /gate/Castor/geometry/setRmin 0. mm
> /gate/Castor/geometry/setRmax 5. mm
> /gate/Castor/placement/setTranslation +2. -0. 0.  mm
>
>  /gate/motherbox/daughters/name Pollux
> /gate/motherbox/daughters/insert cylinder
> /gate/Pollux/geometry/setHeight 20. mm
> /gate/Pollux/geometry/setRmin 0. mm
> /gate/Pollux/geometry/setRmax 5. mm
> /gate/Pollux/placement/setTranslation -2. -0. 0.  mm
>
> these  volumes should have a big overlap at the center of motherbox.
>
> Now what's occuring when a particle pass through the middle of motherbox?
> Is the particle inside of Pollux ?
> Is the particle inside of Pollux and Castor, and can interact with both
> Does the particle belong to the first volume it crossed ?
>
>
> If the last the volume always on-top ?  If yes, this answers myquestion fromyesterday,
>
> the later-declared volume being on-top photons spend more time inside thisone and thus
>  scatter more from the last one.
>
> Cheers,
> Maximilien
>
>  ------------------------------
> *De :* gate-users-bounces at lists.opengatecollaboration.org<javascript:_e(%7B%7D,'cvml','gate-users-bounces at lists.opengatecollaboration.org');>[
> gate-users-bounces at lists.opengatecollaboration.org<javascript:_e(%7B%7D,'cvml','gate-users-bounces at lists.opengatecollaboration.org');>]
> de la part de MELISSAS Maximilien (SAFRAN) [
> maximilien.melissas-alten at safran.fr<javascript:_e(%7B%7D,'cvml','maximilien.melissas-alten at safran.fr');>
> ]
> *Date d'envoi :* mercredi 26 février 2014 15:12
> *À :* gate-users at lists.opengatecollaboration.org<javascript:_e(%7B%7D,'cvml','gate-users at lists.opengatecollaboration.org');>
> *Objet :* [SUSPECTED SPOOFING] [Gate-users] (no subject)
>
>    Dear Gaters,
>
> I am facing an issue I don't understand, with my current description of mysetup, it
>  seems that the X rays scattering depends on the order in which volumes
> have been declared
>
>
>
> To mimic the CT scan of a composite material (I am using Gateto understanda CT-Scan setup usedfor Aeronauticalpart testing),
> I am introducing a periodic network of carbon fiber along each direction
> in my test phantom (Let's call these direction 1, 2, 3)
>
>
>
> If I check the branches ComptVolName and RayleighVolName in the Hit Tree
> , there is always one direction producing more scattering. However
> , whatever the rotation of the phantom, the later-declared direction is
>  always the one producing the most scattered hits.
>
> Here is a pseudo phantom.mac
>
> /gate/world/daughters/name epoxyBox
>
> #Define an epoxy box,
>
> /gate/epoxyBox/daughters/name CCylinder1
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
> /gate/epoxyBox/daughters/name CCylinder2
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
> /gate/epoxyBox/daughters/name CCylinder3
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
>
>
> All the Carbon cylinders are copy-pasted and I change only the
> rotation along X/Y/Z . After running the simulation, if I check whichvolumes producesthe most
>  scattered hits (from Hits/CompVolName and Hits/RayleighVolName) the
> volume producing the most scattered hits is CCylinder3 whatever the
> rotation of the epoxyBox
>
> If now I declare the CCylinder in a different order i.e
>
> /gate/epoxyBox/daughters/name CCylinder3
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
> /gate/epoxyBox/daughters/name CCylinder1
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
> /gate/epoxyBox/daughters/name CCylinder2
>
> #Define and rotate an array of carbon Cylinder using Repeater
>
> Now the CCylinder producing the most scattered hits is CCylinder 2
> (whatever the rotation of the epoxy box)
>
> I made all the rotation testing with few photons (around 100 000) to save
>  Computing time, and I ran another orientation with 10 000 000 photons
> to be sure I am not seeing statistical fluctuations
>
>
>
> Am I misunderstanding the meaning of the Rayleigh/ComptVolName (actually,
> how is this leaf filled when a photon has been scattered several times)?
>  Is it another feature that I don't understand or am I facing a bug?
>
>
>
> Cheers,
>
> Maximilien
>
>
>
> --
>
> Maximilien MELISSAS
>
> Consultant, Alten technology
>
> Image processing for CT NDT @ Safran composite
>
> http://www.alten.com
>
>
>
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-- 
David Sarrut, Phd
Directeur de recherche CNRS
CREATIS, UMR CNRS 5220, Inserm U 1044
Centre de lutte contre le cancer Léon Bérard
28 rue Laënnec, 69373 Lyon cedex 08
Tel : 04 78 78 51 51 / 06 74 72 05 42
http://www.creatis.insa-lyon.fr/~dsarrut
_________________________________
 "2 + 2 = 5,  for extremely large values of 2"
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