The GRS (Grid Support) library has been designed to provide read, write, and manipulation functions for grids and attributes stored on PIF. As a basis for both, generic point list handling services are also provided that deal with orthoProduct and unstructured point lists as well. Both unstructured grids and tensor product grids can be read, written and manipulated, and interpolation of attributes defined on those grids can be performed with this library. New element types for unstructured grids can be introduced easily and are readily available in the generic interpolation routine.
In the following, the architecture of GRS is described first, where the various classes which GRS implements to accomplish its tasks are discussed. The memory-resident structures of GRS objects and their relationships are presented with the help of various figures. Two sections describing the two main purposes GRS was designed for - namely element-wise unstructured grid reading and writing, and generic interpolation of attributes - follow, where many issues of the class designs which looked obscure at the first sight will become clear. Finally, the KIRKPATRICK point location method which is a cornerstone of the unstructured grid interpolation is discussed in more detail.