--- a/Framework/Toolbox/SlicesSorter.cpp	Wed May 15 12:28:58 2019 +0200
+++ b/Framework/Toolbox/SlicesSorter.cpp	Wed May 15 17:30:58 2019 +0200
@@ -285,4 +285,42 @@
 
     return found;
   }
+
+
+  double SlicesSorter::ComputeSpacingBetweenSlices() const
+  {
+    if (GetSlicesCount() <= 1)
+    {
+      // This is a volume that is empty or that contains one single
+      // slice: Choose a dummy z-dimension for voxels
+      return 1.0;
+    }
+    
+    const OrthancStone::CoordinateSystem3D& reference = GetSliceGeometry(0);
+
+    double referencePosition = reference.ProjectAlongNormal(reference.GetOrigin());
+        
+    double p = reference.ProjectAlongNormal(GetSliceGeometry(1).GetOrigin());
+    double spacingZ = p - referencePosition;
+
+    if (spacingZ <= 0)
+    {
+      throw Orthanc::OrthancException(Orthanc::ErrorCode_BadSequenceOfCalls,
+                                      "Please call the Sort() method before");
+    }
+
+    for (size_t i = 1; i < GetSlicesCount(); i++)
+    {
+      OrthancStone::Vector p = reference.GetOrigin() + spacingZ * static_cast<double>(i) * reference.GetNormal();        
+      double d = boost::numeric::ublas::norm_2(p - GetSliceGeometry(i).GetOrigin());
+
+      if (!OrthancStone::LinearAlgebra::IsNear(d, 0, 0.001 /* tolerance expressed in mm */))
+      {
+        throw Orthanc::OrthancException(Orthanc::ErrorCode_BadGeometry,
+                                        "The origins of the slices of a volume image are not regularly spaced");
+      }
+    }
+
+    return spacingZ;
+  }
 }