Partial Water Fill

The geometry uses a trick to allow it to deal with a partially filled detector. This is explained in the Programmer's Manual, but in essence the idea is that it deals with a geometry request ignoring the presence of the D$_2$O and H$_2$O surfaces and then adds them in afterwards. This is completely transparent to the user; with a partially filled detector each fillable region is divided into two parts separated by an optically flat horizontal surface. For fillable region XXX, the region XXX_AIR is the unfilled portion. Both regions support all geometry requests. Note, there are no GEDS or GEDP titles banks for region XXX_AIR; all the information needed comes from the corresponding XXX region.

Partial fill is controlled by the TGEO titles bank. First, comes the flag KTGEO_PARTIAL_FILL that controls this feature. It is followed by two words giving the D$_2$O and H$_2$O levels.