class TGDMLWrite: public TObject

TGDMLWrite Class


This class contains implementation of converting ROOT's gGeoManager
geometry to GDML file. gGeoManager is the instance of TGeoManager class
containing tree of geometries creating resulting geometry. GDML is xml
based format of file mirroring the tree of geometries according to GDML
schema rules. For more information about GDML see http://gdml.web.cern.ch.
Each object in ROOT is represented by xml tag (=xml node/element) in GDML.

This class is not needed to be instanciated. It should always be called
by gGeoManager->Export("xyz.gdml") method. Export is driven by extenstion
that is why ".gdml" is important in resulting name.

Whenever a new ROOT geometry object is implemented or there is a change
in GDML schema this class is needed to be updated to ensure proper mapping
between ROOT objects and GDML elements.

Current status of mapping ROOT -> GDML is implemented in method called
TGDMLWrite::ChooseObject and it contains following "map":

Solids:
TGeoBBox               ->           <box ... >
TGeoParaboloid         ->           <paraboloid ...>
TGeoSphere             ->           <sphere ...>
TGeoArb8               ->           <arb8 ...>
TGeoConeSeg            ->           <cone ...>
TGeoCone               ->           <cone ...>
TGeoPara               ->           <para ...>
TGeoTrap               ->           <trap ...>   or
-                      ->           <arb8 ...>
TGeoGtra               ->           <twistedtrap ...>   or
-                      ->           <trap ...>          or
-                      ->           <arb8 ...>
TGeoTrd1               ->           <trd ...>
TGeoTrd2               ->           <trd ...>
TGeoTubeSeg            ->           <tube ...>
TGeoCtub               ->           <cutTube ...>
TGeoTube               ->           <tube ...>
TGeoPcon               ->           <polycone ...>
TGeoTorus              ->           <torus ...>
TGeoPgon               ->           <polyhedra ...>
TGeoEltu               ->           <eltube ...>
TGeoHype               ->           <hype ...>
TGeoXtru               ->           <xtru ...>
TGeoCompositeShape     ->           <union ...>            or
-                      ->           <subtraction ...>      or
-                      ->           <intersection ...>

Special cases of solids:
TGeoScaledShape        ->           <elcone ...>  if scaled TGeoCone or
-                      ->           element without scale
TGeoCompositeShape     ->           <ellipsoid ...>
-                                   intersection of:
-                                   scaled TGeoSphere and TGeoBBox

Materials:
TGeoIsotope            ->           <isotope ...>
TGeoElement            ->           <element ...>
TGeoMaterial           ->           <material ...>
TGeoMixture            ->           <material ...>

Structure
TGeoVolume             ->           <volume ...>   or
-                      ->           <assembly ...>
TGeoNode               ->           <physvol ...>
TGeoPatternFinder      ->           <divisionvol ...>

There are options that can be set to change resulting document
Options:
g - is set by default in gGeoManager, this option ensures compatibility
-   with Geant4. It means:
-   -> atomic number of material will be changed if <1 to 1
-   -> if polycone is set badly it will try to export it correctly
-   -> if widht * ndiv + offset is more then width of object being divided
-      (in divisions) then it will be rounded so it will not exceed or
-      if kPhi divsion then it will keep range of offset in -360 -> 0
f - if this option is set then names of volumes and solids will have
-   pointer as a suffix to ensure uniqness of names
n - if this option is set then names will not have suffix, but uniqness is
-   of names is not secured
- - if none of this two options (f,n) is set then default behaviour is so
-   that incremental suffix is added to the names.
-   (eg. TGeoBBox_0x1, TGeoBBox_0x2 ...)

USAGE:
gGeoManager->Export("output.gdml");
gGeoManager->Export("output.gdml","","vg"); //the same as previous just
options are set explicitly
gGeoManager->Export("output.gdml","","vgf");
gGeoManager->Export("output.gdml","","gn");
gGeoManager->Export("output.gdml","","f");


NB:
Options discussed above are used only for TGDMLWrite class. There are
other options in the TGeoManager::Export(...) method that can be used.
See that function for details.