From e958704112b0dba32d299e6ab05d1c8a9fee69b6 Mon Sep 17 00:00:00 2001
From: Ben Wibking <ben@wibking.com>
Date: Fri, 21 Mar 2025 12:28:58 -0400
Subject: [PATCH 1/2] write binary VTP particles

---
 .../amrex_particles_to_vtp/write_pview_file.py    | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py b/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
index 253b862db1a..5bda181be8b 100644
--- a/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
+++ b/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
@@ -199,14 +199,17 @@ def write_paraview_file_particles(fname,pts,ncdata):
     outfile.write("</PointData>\n")
 
     outfile.write("<Points>\n")
-    outfile.write("<DataArray type=\"Float32\" Name=\"Points\" NumberOfComponents=\"3\" format=\"ascii\">\n")
-    for i in range(Npts):
-        outfile.write("%e\t%e\t%e\t"%(pts[i][0],pts[i][1],pts[i][2]))
+    outfile.write("<DataArray type=\"Float32\" Name=\"Points\" NumberOfComponents=\"3\" format=\"appended\" offset=\"0\">\n")
     outfile.write("\n</DataArray>\n")
-    outfile.write("</Points>\n")
-
+    outfile.write("</Points>\n")    
     outfile.write("</Piece>\n")
     outfile.write("</PolyData>\n")
-    outfile.write("</VTKFile>\n")
 
+    # write binary data AppendedData
+    outfile.write("<AppendedData>\n")
+    outfile.write("_")
+    outfile.write(pts.tobytes('C')) # use C-ordering of array
+    outfile.write("\n</AppendedData>")
+
+    outfile.write("</VTKFile>\n")
     outfile.close()

From 767d1e2bcc91353eb414ecfc24fecf8a3eb1ecd9 Mon Sep 17 00:00:00 2001
From: Ben Wibking <ben@wibking.com>
Date: Fri, 21 Mar 2025 13:21:53 -0400
Subject: [PATCH 2/2] fix binary write

---
 .../write_pview_file.py                       | 24 +++++++++++++------
 1 file changed, 17 insertions(+), 7 deletions(-)

diff --git a/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py b/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
index 5bda181be8b..57264745432 100644
--- a/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
+++ b/Tools/Py_util/amrex_particles_to_vtp/write_pview_file.py
@@ -1,4 +1,6 @@
 import numpy as np
+import struct
+import os
 
 def write_paraview_file_structmesh(fname,xp,yp,ccdata,ncdata):
 
@@ -184,7 +186,7 @@ def write_paraview_file_particles(fname,pts,ncdata):
     Npts=pts.shape[0]
 
     outfile.write("<?xml version=\"1.0\"?>\n")
-    outfile.write("<VTKFile type=\"PolyData\" version=\"0.1\" byte_order=\"LittleEndian\">\n")
+    outfile.write("<VTKFile type=\"PolyData\" version=\"0.1\" byte_order=\"LittleEndian\" header_type=\"UInt64\">\n")
     outfile.write("<PolyData>\n")
     outfile.write("<Piece NumberOfPoints=\"%d\" NumberOfVerts=\"0\" NumberOfLines=\"0\" NumberOfStrips=\"0\" NumberOfPolys=\"0\">\n"%(Npts))
 
@@ -200,16 +202,24 @@ def write_paraview_file_particles(fname,pts,ncdata):
 
     outfile.write("<Points>\n")
     outfile.write("<DataArray type=\"Float32\" Name=\"Points\" NumberOfComponents=\"3\" format=\"appended\" offset=\"0\">\n")
-    outfile.write("\n</DataArray>\n")
+    outfile.write("</DataArray>\n")
     outfile.write("</Points>\n")    
     outfile.write("</Piece>\n")
     outfile.write("</PolyData>\n")
 
-    # write binary data AppendedData
-    outfile.write("<AppendedData>\n")
-    outfile.write("_")
-    outfile.write(pts.tobytes('C')) # use C-ordering of array
+    # write AppendedData in special format
+    # https://vtk.org/Wiki/VTK_XML_Formats#Uncompressed_Data
+    outfile.write("<AppendedData encoding=\"raw\">\n")
+    outfile.write("\t_")
+    outfile.close()
+    with open(fname, 'ab') as binfile:
+        arrays_to_write = [pts]
+        for arr in arrays_to_write:
+            float_arr = arr.astype(np.float32)
+            binfile.write(struct.pack('<L', arr.nbytes))
+            binfile.write(float_arr.tobytes('C'))
+
+    outfile = open(fname, 'a')
     outfile.write("\n</AppendedData>")
-
     outfile.write("</VTKFile>\n")
     outfile.close()