1 files changed, 9 insertions, 0 deletions
diff --git a/transfer.h b/transfer.h
index bb9a035..d000dcd 100644
--- a/transfer.h
+++ b/transfer.h
@@ -34,8 +34,17 @@ enum GridTransferOperator {
     GRID_TRANSFER_FW_3,
 };
 
+/**
+ * A 2-dimensional grid with regular spacing.
+ */
 typedef struct RegularGrid2D {
     /**
+     * Indices of the grid origin, relative to coordinate origin.
+     * (o0, o1) = (start[0] * step[0], start[1] * step[1])
+     */
+    ptrdiff_t           start[2];
+
+    /**
      * Number of points in the domain.
      */
     size_t              size[2];