diff --git a/SceneGeom.cpp b/SceneGeom.cpp
index e8796b2..829ecec 100644
--- a/SceneGeom.cpp
+++ b/SceneGeom.cpp
@@ -266,7 +266,7 @@ Scene::DrawGeoObj( const IGdbIterator& iIter, int nPass, MdStMk siObj)
          pGraphics->AddMaterial( mMat.GetAmbient(), mMat.GetDiffuse(),
                                  mMat.GetSpecular(), mMat.GetShininess()) ;
          pGraphics->AddBackMaterial( GetSurfBackColor( mMat.GetDiffuse())) ;
-         pGraphics->StartTriangles( pSTM->GetTriangleNum()) ;
+         pGraphics->StartTriangles( pSTM->GetTriangleSize()) ;
         // ciclo sui triangoli della superficie
          Triangle3d Tria ;
          TriNormals3d TNrms ;