better control on cutout

src/anemoi/datasets/data/grids.py

@@ -128,7 +128,7 @@ def tree(self):
 
 
 class Cutout(GridsBase):
-    def __init__(self, datasets, axis, min_distance_km=None, cropping_distance=2.0, plot=False):
+    def __init__(self, datasets, axis, min_distance_km=None, cropping_distance=2.0, neighbours=5, plot=False):
         from anemoi.datasets.grids import cutout_mask
 
         super().__init__(datasets, axis)
@@ -147,6 +147,7 @@ def __init__(self, datasets, axis, min_distance_km=None, cropping_distance=2.0,
             plot=plot,
             min_distance_km=min_distance_km,
             cropping_distance=cropping_distance,
+            neighbours=neighbours,
         )
         assert len(self.mask) == self.globe.shape[3], (
             len(self.mask),
@@ -234,6 +235,7 @@ def cutout_factory(args, kwargs):
     plot = kwargs.pop("plot", None)
     min_distance_km = kwargs.pop("min_distance_km", None)
     cropping_distance = kwargs.pop("cropping_distance", 2.0)
+    neighbours = kwargs.pop("neighbours", 5)
 
     assert len(args) == 0
     assert isinstance(cutout, (list, tuple))
@@ -244,6 +246,7 @@ def cutout_factory(args, kwargs):
     return Cutout(
         datasets,
         axis=axis,
+        neighbours=neighbours,
         min_distance_km=min_distance_km,
         cropping_distance=cropping_distance,
         plot=plot,

src/anemoi/datasets/grids.py

@@ -145,6 +145,7 @@ def cutout_mask(
     global_lats,
     global_lons,
     cropping_distance=2.0,
+    neighbours=5,
     min_distance_km=None,
     plot=None,
 ):
@@ -191,7 +192,8 @@ def cutout_mask(
 
     # Use a KDTree to find the nearest points
     kdtree = KDTree(lam_points)
-    distances, indices = kdtree.query(global_points, k=4)
+
+    distances, indices = kdtree.query(global_points, k=neighbours)
 
     if min_distance_km is not None:
         min_distance = min_distance_km / 6371.0
@@ -213,25 +215,18 @@ def cutout_mask(
         # We check more than one triangle in case te global point
         # is near the edge of triangle, (the lam point and global points are colinear)
 
-        t1 = Triangle3D(lam_points[index[0]], lam_points[index[1]], lam_points[index[2]])
-        t2 = Triangle3D(lam_points[index[1]], lam_points[index[2]], lam_points[index[3]])
-        t3 = Triangle3D(lam_points[index[2]], lam_points[index[3]], lam_points[index[0]])
-        t4 = Triangle3D(lam_points[index[3]], lam_points[index[0]], lam_points[index[1]])
-
-        # The point is inside the triangle if the intersection with the ray
-        # from the point to the centre of the Earth is not None
-        # (the direction of the ray is not important)
-
-        intersect = (
-            t1.intersect(zero, global_point)
-            or t2.intersect(zero, global_point)
-            or t3.intersect(zero, global_point)
-            or t4.intersect(zero, global_point)
-        )
+        inside = False
+        for j in range(neighbours):
+            t = Triangle3D(
+                lam_points[index[j]], lam_points[index[(j + 1) % neighbours]], lam_points[index[(j + 2) % neighbours]]
+            )
+            inside = t.intersect(zero, global_point)
+            if inside:
+                break
 
         close = np.min(distance) <= min_distance
 
-        inside_lam.append(intersect or close)
+        inside_lam.append(inside or close)
 
     j = 0
     inside_lam = np.array(inside_lam)