modifying geometries after gGeoManager->CloseGeometry()

Hello ROOTers,

I would like to know how to modify the shape of a geo volume after calling gGeoManager->CloseGeometry(). What I want to do is to optimize the shape of a TGeoPgon to obtain the maximum collection efficiency of a light guide in my simulation. In the optimization process, I would like to tweak the shape the TGeoPgon slightly but other volume will not be changed.

Do I have to re-build all volumes again? or is there any way to change the shape after closing the geometry as following example?

gGeoManager->CloseGeometry();
(some simulation code here)

gGeoManager->ReopenGeometry(); // I could not a similar method myPgonVolume->DefineSection(i, z, rmin, rmax); // change the shape of a Pgon gGeoManager->CloseGeometry(); // close again
(some simulation code here again)

Regards,

--
OKUMURA, Akira oxon@{astro.isas.jaxa.jp,stanford.edu}
Institute of Space and Astronautical Science (ISAS/JAXA)
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