// called by sectors:
 inline void AddVisibleDecorationInstance(VTerrainDecorationInstance *pInstance)
 {
   IVTerrainDecorationModel *pModel = pInstance->m_spModel;
   VASSERT(pModel!=NULL);
   if (VISION_UNLIKELY(!pModel->IsLoaded()))
   {
     if (pModel->IsMissing())
       return;
     pModel->EnsureLoaded();
     if (pModel->IsMissing() || !pModel->IsValid())
       return;
   }
   pModel->UpdateTimeStamp(); // for resource management
   m_VisibleDecoration[m_iVisibleDecorationCount++] = pInstance;
 }