diff --git a/python_tools/void_python_tools/partUtil/partUtil.py b/python_tools/void_python_tools/partUtil/partUtil.py
index a1def0e..055d0ca 100644
--- a/python_tools/void_python_tools/partUtil/partUtil.py
+++ b/python_tools/void_python_tools/partUtil/partUtil.py
@@ -26,6 +26,7 @@ import sys
 from void_python_tools.backend import *
 import void_python_tools.apTools as vp
 import pickle
+from periodic_kdtree import PeriodicCKDTree
 
 NetCDFFile = Dataset
 ncFloat = 'f8'
@@ -135,6 +136,27 @@ def loadPartVel(sampleDir):
 
     return partVel
 
+# -----------------------------------------------------------------------------
+def getPartTree(sampleDir, partData, boxLen):
+
+  with open(sampleDir+"/sample_info.dat", 'rb') as input:
+    sample = pickle.load(input)
+
+  periodicLine = getPeriodic(sample)
+
+  periodic = 1.*boxLen
+
+  if not "x" in periodicLine: periodic[0] = -1
+  if not "y" in periodicLine: periodic[1] = -1
+  if not "z" in periodicLine: periodic[2] = -1
+
+  return PeriodicCKDTree(periodic, partData)
+
+# -----------------------------------------------------------------------------
+def getBall(partTree, center, radius):
+
+  return partTree.query_ball_point(center, r=radius)
+
 
 # -----------------------------------------------------------------------------
 def shiftPart(inPart, center, periodicLine, ranges):