diff --git a/src/treelayout.cpp b/src/treelayout.cpp
new file mode 100644
index 0000000..c1fecf3
--- /dev/null
+++ b/src/treelayout.cpp
@@ -0,0 +1,31 @@
+/* -*- Mode:C++; c-file-style:"gnu"; indent-tabs-mode:nil -*- */
+/*
+ * Copyright (c) 2013, Regents of the University of California
+ *                     Yingdi Yu
+ *
+ * BSD license, See the LICENSE file for more information
+ *
+ * Author: Zhenkai Zhu <zhenkai@cs.ucla.edu>
+ *         Alexander Afanasyev <alexander.afanasyev@ucla.edu>
+ */
+
+#include "treelayout.h"
+
+void
+OneLevelTreeLayout::setOneLevelLayout(std::vector<Coordinate> &childNodesCo)
+{
+  if (childNodesCo.empty())
+  {
+    return;
+  }
+  double y = getLevelDistance();
+  double sd = getSiblingDistance();
+  int n = childNodesCo.size();
+  double x = - (n - 1) * sd / 2;
+  for (int i = 0; i < n; i++)
+  {
+    childNodesCo[i].x = x;
+    childNodesCo[i].y = y;
+    x += sd;
+  }
+}