openPMD: Generalize Mesh Position (#1296)

This adds a small utility that returns the relative in-cell position of values
on each cell depending on an `amrex::MultiFab`'s `Box`'s `IndexType`.

This does not change the output of openPMD yet, since we spatially and
temporally center fields before output, but makes the routines
more general overall for future use.

1 files changed, 31 insertions, 0 deletions

diff --git a/Source/Utils/RelativeCellPosition.H b/Source/Utils/RelativeCellPosition.H
new file mode 100644
index 000000000..15ec06707
--- /dev/null
+++ b/Source/Utils/RelativeCellPosition.H
@@ -0,0 +1,31 @@
+/* Copyright 2020 Axel Huebl
+ *
+ * This file is part of WarpX.
+ *
+ * License: BSD-3-Clause-LBNL
+ */
+#ifndef WARPX_RELATIVE_CELL_POSITION_H_
+#define WARPX_RELATIVE_CELL_POSITION_H_
+
+#include "WarpX.H"
+
+#include <AMReX_MultiFab.H>
+
+#include <vector>
+
+
+namespace utils
+{
+    /** Get the Relative Cell Position of Values in an MultiFab
+     *
+     * Translate the IndexType of a given MultiFab into a position relative to
+     * the lower corner of a cell.
+     *
+     * @param[in] mf the amrex::MultiFab to get relative cell positions for
+     * @return relative position to the lower corner, scaled to cell size [0.0:1.0)
+     */
+    std::vector< double >
+    getRelativeCellPosition (amrex::MultiFab const& mf);
+}
+
+#endif // WARPX_RELATIVE_CELL_POSITION_H_