typedef enum {
   MPIPathElementTypeINVALID,
   MPIPathElementTypeARC,           /* only 2D */
   MPIPathElementTypeARC_CENTER,    /* only 2D */
   MPIPathElementTypeARC_END_POINT, /* both 2D and 3D */
   MPIPathElementTypeHELIX,         /* not currently supported */
   MPIPathElementTypeIO,            /* not currently supported */
   MPIPathElementTypeLINE,          /* both 2D and 3D */

	MPIPathElementTypeMASK,
} MPIPathElementType;