diff --git a/c_tools/mock/loaders/gadget_loader.cpp b/c_tools/mock/loaders/gadget_loader.cpp
index a76416a..ff7fd17 100644
--- a/c_tools/mock/loaders/gadget_loader.cpp
+++ b/c_tools/mock/loaders/gadget_loader.cpp
@@ -71,32 +71,7 @@ public:
     d->BoxSize *= unitMpc;
 
     applyTransformations(d);
-
-    long numAccepted = 0;
-    bool *accepted = new bool[d->NumPart];
-    for (long i = 0; i < d->NumPart; i++)
-      {
-	SingleParticle p;
-
-	for (int k = 0; k < 3; k++)
-	  {
-	    p.Pos[k] = (d->Pos[k]) ? 0 : d->Pos[k][i];
-	    p.Vel[k] = (d->Vel[k]) ? 0 : d->Vel[k][i];
-	  }
-	p.ID = (d->Id) ? 0 : d->Id[i];
-	
-	accepted[i] = preproc->accept(p);
-	numAccepted += accepted[i];
-      }
-    
-    for (int k = 0; k < 3; k++)
-      {
-	filteredCopy(d->Pos[k], accepted, d->NumPart);
-	filteredCopy(d->Vel[k], accepted, d->NumPart);
-      }
-    filteredCopy(d->Id, accepted, d->NumPart);
-    filteredCopy(d->type, accepted, d->NumPart);
-    delete[] accepted;
+    basicPreprocessing(d, preproc);
 
     return d;
   }
diff --git a/c_tools/mock/loaders/simulation_loader.cpp b/c_tools/mock/loaders/simulation_loader.cpp
index 7befab0..864e19a 100644
--- a/c_tools/mock/loaders/simulation_loader.cpp
+++ b/c_tools/mock/loaders/simulation_loader.cpp
@@ -39,3 +39,35 @@ void SimulationLoader::applyTransformations(SimuData *s)
 	redshift_gravity*s->Vel[redshift_axis][i]/100.;
     }
 }
+
+
+void SimulationLoader::basicPreprocessing(SimuData *d, 
+                                          SimulationPreprocessor *preproc)
+{
+    long numAccepted = 0;
+    bool *accepted = new bool[d->NumPart];
+    for (long i = 0; i < d->NumPart; i++)
+      {
+	SingleParticle p;
+
+	for (int k = 0; k < 3; k++)
+	  {
+	    p.Pos[k] = (d->Pos[k]) ? 0 : d->Pos[k][i];
+	    p.Vel[k] = (d->Vel[k]) ? 0 : d->Vel[k][i];
+	  }
+	p.ID = (d->Id) ? 0 : d->Id[i];
+	
+	accepted[i] = preproc->accept(p);
+	numAccepted += accepted[i];
+      }
+    
+    for (int k = 0; k < 3; k++)
+      {
+	filteredCopy(d->Pos[k], accepted, d->NumPart);
+	filteredCopy(d->Vel[k], accepted, d->NumPart);
+      }
+    filteredCopy(d->Id, accepted, d->NumPart);
+    filteredCopy(d->type, accepted, d->NumPart);
+    delete[] accepted;
+
+}
diff --git a/c_tools/mock/loaders/simulation_loader.hpp b/c_tools/mock/loaders/simulation_loader.hpp
index e03b385..6fdb462 100644
--- a/c_tools/mock/loaders/simulation_loader.hpp
+++ b/c_tools/mock/loaders/simulation_loader.hpp
@@ -40,6 +40,8 @@ protected:
 
   void reallocSimu(CosmoTool::SimuData *s, long newNumPart);
  
+
+  void basicPreprocessor(SimuData *d, SimulationPreprocessor *preproc);
   void applyTransformations(CosmoTool::SimuData *s);
 
   void copyParticleToSimu(const SingleParticle& p, CosmoTool::SimuData *s, long index)