Add more data from the grid

The forward/backward_{R,Z} are needed for field line tracing

Author: dschwoerer

xbout/geometries.py

@@ -495,7 +495,16 @@ def add_s_alpha_geometry_coords(ds, *, coordinates=None, grid=None):
 @register_geometry("fci")
 def add_fci_geometry_coords(ds, *, coordinates=None, grid=None):
     assert coordinates is None, "Not implemented"
-    ds = _add_vars_from_grid(ds, grid, ["R", "Z"])
+
+    keys = sum(
+        [
+            [f"{pre}R", f"{pre}Z", f"{pre}xt_prime", f"{pre}zt_prime"]
+            for pre in ["forward_", "backward_"]
+        ],
+        [],
+    )
+
+    ds = _add_vars_from_grid(ds, grid, ["R", "Z"], optional_variables=keys + ["B"])
     ds = ds.set_coords(("R", "Z"))
     ds = _create_single_region(ds, periodic_y=True)
     return ds