Follow-up from "3D Implants, Many"
The following discussions from !672 (merged) should be addressed:
Geant4 implementation to allow for materials other than Silicon:
-
@slachnit started a discussion: (+1 comment) The excising is done using a
G4MultiUnion
, but since implants can overlap between pixel cells (think of an ohmic column in the pixel corner) they individual implants should be calculated from aG4IntersectionSolid
between the pixel cell and the implant volume. With this, theG4MultiUnion
at least fails to render, not sure if tracking is fine.Ok so basically this boils entirely down to the fact that implants can overlap between pixel cells, because otherwise using a daughter volume is completely fine and does not require a
G4MultiUnion
whatsoever.I think we should probably avoid using the
G4MultiUnion
approach, the performance costs do not scale. And cutting away the implant from the pixel in G4 also feels like nasty cheating to me.I think we have the following options:
- a) don't support implants overlapping between pixels cells for now
This would be the easiest, but I'm not sure how important this is. We can always come back later to this. In this approach we would just create daughter implants in the pixel cell - when we then replicate the pixels over the sensor.
Thing is, we don't actually build the pixels in Geant4 - not sure why? I assume there is a tiny performance boost? The comment in the code is not very descriptive.
Anyway, we can still do this without a changing of our G4 stuff by only replicating the implants. But then we might as well just add the pixel cells, I doubt there is a noticeable performance impact on top.
- b) actually allow overlapping since we don't build pixel cells anyway
Same as a), we only need to detect pixels on the edge and use a IntersectionSoild for the implant there if it overlaps the sensor volume.
- c) cut the implants into pixel cells
Same as a) basically, but we cut overlapping implants to pixel cell size and then replicate pixel cells.
Implementation for e.g. radial strips:
-
@slachnit started a discussion: (+1 comment) Not sure actually but we wouldn't be able to create this bend implants, right?