Coordinates

The flesh provides utility routines for registering and querying coordinate information. The flesh does not provide any coordinates itself, these must be supplied by a thorn. Thorns are not required to register coordinates to the flesh, but registering coordinates provides a means for infrastructure thorns to make use of coordinate information.

Coordinates are grouped into coordinate systems, which have a specified dimension. Any number of coordinate systems can be registered with the flesh, and a coordinate system must be registered before any coordinates can be registered, since they must be associated with their corresponding system. Coordinates can be registered, with any chosen name, with an existing coordinate system, along with their direction or index in the coordinate system. Optionally, the coordinate can also be associated with a given grid variable. A separate call can register the global range for a coordinate on a given grid hierarchy.

Following conventions for coordinate system and coordinate names, provides a means for other thorns to use the physical properties of coordinate systems, without being tied to a particular thorn.

A registered coordinate system can be referred to by either its name or an associated integer known as a handle. Passing a handle instead of the name string may be necessary for calling C routines from Fortran.