DESCRIPTION:

Many renderers in Eccet require precalculated normal direction
information to work properly. Therefore each volume usually
has a field attached to carry this normal information.

As the normal information is usually not required when segmenting
or in inner areas this field is normally overloaded with the grey
field (see there).

The field has a type of (see fieldtype) U16, i.e. an unsigned
short integer with an allowed value range of 0-65535 and is called
"Norm".