modified: src/BarrelTrackerWithFrame_geo.cpp

src/BarrelTrackerWithFrame_geo.cpp

@@ -120,7 +120,7 @@ static Ref_t create_detector(Detector& description, xml_h e, SensitiveDetector s
     volumes[m_nam] = m_vol;
     m_vol.setVisAttributes(description.visAttributes(x_mod.visStr()));
 
-    double thickness_sum = total_thickness/2.0;
+    double thickness_sum = -total_thickness/2.0;
     for (xml_coll_t ci(x_mod, _U(module_component)); ci; ++ci, ++ncomponents) {
       xml_comp_t x_comp = ci;
       xml_comp_t x_pos  = x_comp.position(false);