A Retrospective On the NuGraf Interface

In retrospect, the power and generality of the NuGraf Interface comes from the use of this variable-length parameter passing protocol since an application only has to specify the clauses that it would like to change or inquire about; all unspecified parameters are either set to predefined default values or to those previously set by the application. For example, an application can quickly add a ‘point’ light source just by specifying the ‘Nt_MODEL,Nt_POINT’ clause as shown in the first example of this section; all other 8 sub-options of the point light source model will be defaulted to appropriate values unless otherwise specified in the argument list (2 of the 8 sub-options are shown in the example).

And unlike other interfaces, such as PHIGS, an application program can pass dozens or hundreds of data items across the interface using a single function call rather than hundreds of function calls (this makes for considerably shorter programs which are more readable). Furthermore, as the functionality of the library grows, the interface can be easily changed to accommodate the growth by adding new clauses to existing interface functions; such changes will not require the addition of new function calls nor require changes to existing NuGraf application programs.