Add pre-transposed lfric rotations

Author: mo-jonasganderton

src/atlas/grid/detail/grid/CubedSphere2.cc

@@ -120,7 +120,7 @@ PointXYZ CubedSphere2::tangent_to_xyz_coord(const PointXY& tan_coord, idx_t tile
 
     tan_point << tan_coord[0], tan_coord[1], 1;
 
-    xyz = lfric_rotations_[tile].transpose() * tan_point;
+    xyz = lfric_rotations_transposed_[tile] * tan_point;
     xyz.normalize();
 
     return {xyz(0), xyz(1), xyz(2)};

src/atlas/grid/detail/grid/CubedSphere2.h

@@ -181,6 +181,15 @@ class CubedSphere2 : public Grid {
         Matrix({{-1, 0, 0}, {0, -1, 0}, {0, 0, -1}})
     };
 
+    std::array<Matrix, 6> lfric_rotations_transposed_ = {
+        Matrix({{0, 0, 1}, {1, 0, 0}, {0, -1, 0}}),
+        Matrix({{-1, 0, 0}, {0, 0, 1}, {0, -1, 0}}),
+        Matrix({{0, 0, -1}, {-1, 0, 0}, {0, -1, 0}}),
+        Matrix({{1, 0, 0}, {0, 0, -1}, {0, -1, 0}}),
+        Matrix({{-1, 0, 0}, {0, 1, 0}, {0, 0, 1}}),
+        Matrix({{-1, 0, 0}, {0, -1, 0}, {0, 0, -1}})
+    };
+
 };
 
 }  // namespace grid