Each class derived from SoSField begins with an SoSF prefix and contains one value of a particular type. Each has setValue() and getValue() methods that are used to change or access this value. In addition, some field classes have extra
convenience routines that allow values to be set or retrieved in other related formats (see below).
In addition to setValue(), all single-value fields overload the "=" assignment operator to set the field value from the correct datatype or from another field instance of the same type.
The value of a single-value field is written to file in a format dependent on the field type; see the
subclass man pages for details.
A field that is ignored has a tilde (~) either in place of the value (if the actual value is the default) or after it (otherwise).