C++ example to access edges and trims of a given brep face

  //Given a brep and a face index
  const ON_Brep* brep;
  const int face_index = 0;
  ON_SimpleArray<int> face_ti_list; //trims indeces list
  ON_SimpleArray<int> face_ei_list; //edges indeces list


  //Get the BrepFace of the given index
  const ON_BrepFace* face = brep->Face(face_index);
  if( 0 == face )
    return false;


  //Get the loop of the face
  for( int fli = 0; fli < face->LoopCount(); fli++ )
  {
    const ON_BrepLoop* loop = face->Loop( fli );
    if( 0 == loop )
      continue;


    for( int lti = 0; lti < loop->TrimCount(); lti++ )
    {
      //Find the trim
      const ON_BrepTrim* trim = loop->Trim( lti );
      if( 0 == trim )
        continue;
      face_ti_list.Append( trim->m_trim_index );


      //Find the edge of that trim
      //Each trim has exactly one edge attached to it
      const ON_BrepEdge* edge = trim->Edge();
      if( 0 == edge )
        continue;
      face_ei_list.Append( edge->m_edge_index );
    }
  }

C++ example that finds edges and faces surrounding a given brep vertex

  //Given a brep and a vertex index
  const ON_Brep* brep;
  const int vertex_index = 0;
  ON_SimpleArray<int> face_i_list; //faces indeces list
  ON_SimpleArray<int> edge_i_list; //edges indeces list


  //Get the vertex;
  const ON_BrepVertex* vertex = brep->Vertex( vertex_index );
  if( 0 == vertex )
    return false;


  //Find surrounding edges
  for( int i = 0; i < vertex->EdgeCount(); i++ )
  {
    int edge_index = vertex->m_ei[i];
    const ON_BrepEdge* edge = brep->Edge( edge_index );
    if( 0 == edge )
      continue;


    //Add to edges list
    edge_i_list.Append( edge_index );


    //Find all trims connected to the edge
    for( int eti = 0; eti < edge->TrimCount(); eti++ )
    {
      const ON_BrepTrim* trim = edge->Trim( eti );
      if( 0 == trim )
        continue;


      ON_BrepLoop* loop = trim->Loop();
      if( 0 == loop )
        continue;


      ON_BrepFace* face = loop->Face();
      if( 0 == face )
        continue;


      //Add to faces list
      face_i_list.Append( face->m_face_index );
    }
  }