Chroma COLLADA
================

Current G4DAE material handling are just names, need:

#. implement the GDML G4 material (and surface) wavelength array 
   properties into COLLADA extra tags

#. hmm maybe GDML does not cover wavelength dependant props, will need to 
   devise xml format and handling for that 


GDML wavelength dependant properties
---------------------------------------

* http://lcgapp.cern.ch/project/simu/framework/GDML/doc/GDMLmanual.pdf

* :google:`optical surfaces gdml`
* :google:`gdml wavelength dependant properties`

* http://microboone-docdb.fnal.gov/cgi-bin/RetrieveFile?docid=1000;filename%3DTDRFinal.pdf;version%3D1


* http://geant4.cern.ch/support/ReleaseNotes4.9.3.html

GDML: it is now possible to customise the reader as well as the writer to treat
ad-hoc user extensions to the GDML schema. The GDML writer now also supports
dumping of optical surface properties associated with surfaces and materials.


* http://www-geant4.kek.jp/lxr/source/persistency/gdml/schema/
* http://www-geant4.kek.jp/lxr/source/persistency/gdml/schema/gdml.xsd