Hi Chris
be aware that there is no close formula at all for generic quadratic
surfaces for the minimum distance, only approximated ones are available.
Ciao
Alfredo
+----------------------------------------------------------------------+
| Alfredo Ferrari || Tel.: +41.22.76.76119 |
| CERN-EN/STI || Fax.: +41.22.76.69474 |
| 1211 Geneva 23 || e-mail: Alfredo.Ferrari_at_cern.ch |
| Switzerland || |
+----------------------------------------------------------------------+
On Thu, 13 Jul 2017, Chris Theis wrote:
> Hi Anton,
> Thanks for the info. If you could tell me the name of the intersection
> routine then I can implement the rest myself.
>
> Cheers
> Chris
>
>
> On 13 Jul 2017, at 11:21, Anton Lechner <Anton.Lechner_at_cern.ch>
> wrote:
>
>
> For a particle step - in particular for charged particle steps which
> are small - one often does not need an accurate value, but an
> approximate value can be sufficient. This approximate value can be
> smaller than the real minimum distance, but can give an advantage in
> CPU time as it can be much faster calculated than a more accurate
> value (which can anyway not always be obtained analytically). This
> distance is accessible in the variable (DDNEAR) in the common CMMDNR,
> but depending on the type of body, it might only be a rough estimate
> (smaller than the real minimum) or it is not calculated at all (in the
> latter case it is set to zero). If this distance zero or if it is
> smaller than the step length, then the geometry tracker is used to
> propagate the particle, but also in this case one does not need the
> minimum distance but one needs to determine the intersection with a
> surface in the particle direction (while the minimum distance can
> theoretically be in the opposite direction).
>
>
> ---------------------------------------------------------------------------
> ------------------
> Chris Theis
> CERN/HSE-RP - European Organization for Nuclear Research
> 1211 Geneva 23, Switzerland
> Phone: +41 22 767 8069 Office: 892-2A-015
> e-mail: Christian.Theis_at_cern.ch www: http://www.cern.ch/theis
> ---------------------------------------------------------------------------
> ------------------
>
>
>
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Received on Thu Jul 13 2017 - 14:47:15 CEST