diff --git a/Detectors/Base/test/buildMatBudLUT.C b/Detectors/Base/test/buildMatBudLUT.C
index 243a0c60ded6f..85f8343a2d35d 100644
--- a/Detectors/Base/test/buildMatBudLUT.C
+++ b/Detectors/Base/test/buildMatBudLUT.C
@@ -17,8 +17,6 @@
 #include "DetectorsBase/MatLayerCyl.h"
 #include "DetectorsBase/GeometryManager.h"
 #include "ITSMFTReconstruction/ChipMappingITS.h"
-#include "ITS3Simulation/DescriptorInnerBarrelITS3.h"
-#include "ITS3Base/SpecsV2.h"
 #include "CommonUtils/NameConf.h"
 #include <TFile.h>
 #include <TSystem.h>
@@ -31,7 +29,7 @@ o2::base::MatLayerCylSet mbLUT;
 
 bool testMBLUT(const std::string& lutFile = "matbud.root");
 
-bool buildMatBudLUT(int nTst = 60, int maxLr = -1, const std::string& outFile = "matbud.root", const std::string& geomName = "o2sim_geometry-aligned.root");
+bool buildMatBudLUT(int nTst = 30, int maxLr = -1, const std::string& outFile = "matbud.root", const std::string& geomNamePrefix = "o2sim", const std::string& opts = "");
 
 struct LrData {
   float rMin = 0.f;
@@ -46,14 +44,17 @@ struct LrData {
 std::vector<LrData> lrData;
 void configLayers();
 
-bool buildMatBudLUT(int nTst, int maxLr, const std::string& outFile, const std::string& geomNameInput)
+bool buildMatBudLUT(int nTst, int maxLr, const std::string& outFile, const std::string& geomNamePrefix, const std::string& opts)
 {
-  auto geomName = o2::base::NameConf::getGeomFileName(geomNameInput);
+  auto geomName = o2::base::NameConf::getGeomFileName(geomNamePrefix);
   if (gSystem->AccessPathName(geomName.c_str())) { // if needed, create geometry
-    std::cout << geomName << " does not exist. Will create it\n";
-    gSystem->Exec("$O2_ROOT/bin/o2-sim -n 0 --detectorList ALICE2.1");
+    std::cout << geomName << " does not exist. Will create it on the fly\n";
+    std::stringstream str;
+    // constructing an **unaligned** geom (Geant3 used since faster initialization) --> can be avoided by passing an existing geometry
+    str << "${O2_ROOT}/bin/o2-sim-serial -n 0 -e TGeant3 --configKeyValues \"" << opts << "\" --field 0  -o " << geomNamePrefix;
+    gSystem->Exec(str.str().c_str());
   }
-  o2::base::GeometryManager::loadGeometry(geomNameInput);
+  o2::base::GeometryManager::loadGeometry(geomNamePrefix);
   configLayers();
 
   if (maxLr < 1) {
@@ -63,7 +64,7 @@ bool buildMatBudLUT(int nTst, int maxLr, const std::string& outFile, const std::
   }
   for (int i = 0; i < maxLr; i++) {
     auto& l = lrData[i];
-    printf("L:%3d %6.4f<R<%6.4f ZH=%5.4f | dz = %6.4f drph = %6.4f\n", i, l.rMin, l.rMax, l.zHalf, l.dZMin, l.dRPhiMin);
+    printf("L:%3d %6.2f<R<%6.2f ZH=%5.1f | dz = %6.2f drph = %6.2f\n", i, l.rMin, l.rMax, l.zHalf, l.dZMin, l.dRPhiMin);
     mbLUT.addLayer(l.rMin, l.rMax, l.zHalf, l.dZMin, l.dRPhiMin);
   }