diff --git a/SceneGeom.cpp b/SceneGeom.cpp
index f5df0ba..623e217 100644
--- a/SceneGeom.cpp
+++ b/SceneGeom.cpp
@@ -465,6 +465,8 @@ Scene::DrawGeoObj( const IGdbIterator& iIter, int nPass, const MdStMkCol& siObj)
          int nCount = 0 ;
         // numero di colori
          const int ZMAP_COL = 2 ;
+        // indicazione se tridexel
+         bool bIsTriDexel = pZmap->IsTriDexel() ;
         // se triangoli da disegnare
          if ( ( m_nShowZmap & ZSM_SURF) != 0) {
            // definizione materiali
@@ -524,7 +526,7 @@ Scene::DrawGeoObj( const IGdbIterator& iIter, int nPass, const MdStMkCol& siObj)
                   for ( const auto& Tria : vTria) {
                      if ( ( j == 0  &&  Tria.GetGrade() != 0)  ||  ( j == 1  &&  Tria.GetGrade() == 0))
                         continue ;
-                     if ( m_bShowTriaAdvanced)
+                     if ( m_bShowTriaAdvanced  &&  bIsTriDexel)
                         pGraphics->AddTriangle( Tria, Tria.GetTriFlags(), Tria.GetTriNormals()) ;
                      else
                         pGraphics->AddTriangle( Tria, TriFlags3d(), TriNormals3d( Tria.GetN())) ;