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Keywords: Geometry
Forum: Geometry
Re: Question Is it possible to change the geometry during the tracking of a particle? (Wang Yue)
Date: 20 Feb, 2007
From: John Apostolakis <John Apostolakis>

Dear Wang Yue,

Your question is a fundamental one for the geometry modeler. The answer is:

It is not allowed to change or update any volume within a run.

The geometry is 'closed' once the beam is On (/run/beamOn). This step creates a cache of information, which is used during tracking to optimise the number of calls to volumes (and thus execution time).

So we cannot guarantee the behaviour of the simulation if a parameterised volume's, or any volume geometrical attributes are changed by the user. For most potential changes, the results will be wrong.

The information must remain unchanged by the user during the tracking of a particle, an event and all the events of a run.

I do note that a parameterised volume will have its ComputeTransformation, ComputeSolid (etc) methods called, and that the volume in memory will be changed to reflect the different copy/replica number of each volume. But copy number 1 must always be the same, as must all other copies - they cannot be different for one particle or one type of particle.

If you need to make changes there are a few possibilities:
 - run a set of events with one geometry, and then change it;
 - if you need to have a different geometry for one particle type, you
could create a custom solution.

Please do explain what you want to do, so that we can provide further advise or suggestions.

Best regards, John Apostolakis

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1 None: Re: Is it possible to change the geometry during the tracking of a particle?   (Wang Yue - 20 Feb, 2007)
(_ Feedback: Re: Is it possible to change the geometry during the tracking of a particle?   (John Apostolakis - 20 Feb, 2007)
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