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Keywords: voxel number, human model
Forum: Medical Applications
Re: Question how many voxels can geant4 includes? (John)
Re: None Re: how many voxels can geant4 includes? (Joseph Perl)
Re: None Re: how many voxels can geant4 includes? (John)
Date: 19 May, 2004
From: Makoto Asai <Makoto Asai>

 For such use-cases, I suggest to use parametrized volume of uniform
cell size, i.e. only material for each cell is parametrized in terms
of copy number. In this case, the maximum number of cells is limitted
by the 32-bit integer, i.e. 2^31 ~ 2*10^9, for their unique copy 
numbers. While, once you adopt three-dimentional parametrization, i.e.
slicing the world volume along x, y and z axes sequentially, you will
have a set of three copy numbers. In this case, you can have almost
infinit number of cells. 

 Real limitation should be the size of a vector mapping a copy number
to corresponding material. For each cell, you need one pointer (size
is equal to one integer) to G4Material object. Let's assume you will
simulate 1 cubic meter of volume with 2*2*2 mm^3 cells. Then, you
need a one-dimentional arey of 10^8 pointers, i.e. 400 MBytes of
memory, for this mapping table.

 On the other hand, even for such huge simulation volume, each primary
particle and its daughters won't see the whole body, but just a small 
potion. Thus, once you adopt a bit of tricks, for example loading
only a portion of the pointer vector to memory, you can reduce the
size of your executable significantly.

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1 Idea: Detailed tips   (Makoto Asai - 13 Oct, 2004)
3 None: Re: how many voxels can geant4 includes?   (Andrew Prideaux - 30 Apr, 2007)
1 None: Changing Density for a Material   (Joseph Perl - 04 May, 2007)
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