From Andrei and Mihaela Gheata:

New package to edit/create detector geometries

1. Using the geombuilder with a geometry from scratch:

root[0] new TGeoManager("test", "test geometry builder");
root[1] gGeoManager->Edit();

In this case forcing TGeoManager::Edit() is mandatory because the geometry cannot be yet drawn in the pad. There are few steps to create a valid geometry:
- create at least one material from the "Materials" shutter item category. Generally for creating objects, the interface is always in the TGeoManagerEditor in different categories - one should just provide a name and requested params.
- create a shape for the top volume within the "Shapes" category. For the moment the shapes that have editors are: Box, Trd1, Trd2, Tube, Tube segment, Cone, Cone segment and Sphere. More to come...
- create a medium from one of the existing materials from the "Medium" category. You will notice that some categories as: "Volume" and "Medium" are inactive at the beginning because at that time there is no material yet (for making a medium) and no shape (for making a volume). These categories are dynamically activated once all the required components are defined.
- create a volume from the "Volumes" category. You will notice that contrary to the other editors, the volume editor is opened in a tab, not transient - this is because it is more complex.
- go back to "General" category and select the newly created volume as the top one (you can do it also from the volume category)


This is just to start. To create really some hierarchy, one has to create several other volumes and the matrices to position them. Once this is done, use the volume editor interface to:
- add/remove daughters, change shape, edit position of daughters
- change visualization settings
- divide the volume (only if there are no daughters yet)

The TGeoManagerEditor GUI allows:
- editing the geometry name/title, setting top volume, closing the geometry, exporting the geometry as .root or .C file
- creation of new elements (shapes, volumes, materials, media, matrices)
- editing existing elements (they can be browsed from transient dialogs)

IMPORTANT: To access the manager editor if this is not in the "Style" tab one can either:
- left-click on the top-right corner of the pad if something is drawn
- call gGeoManager->Edit()

2. Editing an existing geometry (probably you should start with this first)

- Just load the geometry in memory:
     root[0] .x $ROOTSYS/tutorials/rootgeom.C
-  draw some volume (if not already) then do View/Editor, then click on the top-right corner to get the manager editor. Clicking a volume will open the volume editor in the Style tab, but here I could not get rid of the TAttFill editor that is useless for volumes.
- work with existing TGeoManagerEditor categories as explained at 1.


git-svn-id: http://root.cern.ch/svn/root/trunk@15405 27541ba8-7e3a-0410-8455-c3a389f83636