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None Performance of homogeneous voxelised phantom 

Forum: Geometry
Date: 08 Nov, 2007
From: Sven Lotze <sven>


in my simulation I have a homogeneous water phantom voxelised in 
3d by dividing the box geometry into many G4Boxes in the tracking
geometry and attaching a primitive scorer for deposited energy
to each. As I increase the resolution (smaller voxels), calculation 
time skyrockets.

After some reading, I realise that my implementation is probably
worst case as performance is concerned, because the tracking has
to stop at every voxel boundary. The alternatives I see now are

A) using a parallel readout geometry and do the scoring there, 
   like e.g. in the hadrontherapy example

B) doing it manually by using G4UserStepping action, like
   in TestEM11/12.

I would assume that B should be faster, as more low level
G4 functions are used - is that correct?

On the other hand, as I have to limit the step length as
done in TestEM11/12 according to voxel size, doesn´t that
lead to the same problems as my original geometry with 
small volumes limiting the steps?

Looking at TestEM11/12, for the deposited energy in each 
step a position along the step is randomly chosen before
filling it to a histogram. Why is that necessary if max.
step size is limited corresponding to voxel (=bin) size 
anyway? Why not deposit it at the center of the step?

Thanks for your help!


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1 None: RE: Performance of homogeneous voxelised phantom   (Makoto Asai - 08 Nov, 2007)
1 None: RE: Performance of homogeneous voxelised phantom   (Sven Lotze - 09 Nov, 2007)
2 None: Re: Performance of homogeneous voxelised phantom   (michel maire - 09 Nov, 2007)
1 None: Re: Performance of homogeneous voxelised phantom   (Sven Lotze - 27 Nov, 2007)
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