Also See

How To: Insert a Block

Summary

The process of inserting a block instance using the Rhino 4.0 SDK is identical to that of the Rhino 3.0 SDK. But, the process for dynamically drawing block instances has change. Thus, if you want to allow the user to interactively place the block instance, then you will want to study the code below.

Dynamically Drawing the Block

In order to dynamically draw a block instance in Rhino 3.0, you had to obtain all of the block instance's definition geometry and draw this geometry yourself in either a dynamic drawing operation, such as in CRhinoGetPoint, or in a draw callback.

In Rhino 4.0, we can take advantage of the new display pipleline technology, which is capable of drawing block instance definitions. For example, the following code demonstrates how to draw a block instance definition from a CRhinoGetPoint-derived object's DynamicDraw member.

  class CGetBlockInsertPoint : public CRhinoGetPoint
  {
  public:
    CGetBlockInsertPoint( const CRhinoInstanceDefinition* idef );


    // CRhinoGetPoint overrides
    void OnMouseMove( CRhinoViewport&, UINT, const ON_3dPoint&, const CPoint* );
    void DynamicDraw( HDC, CRhinoViewport&, const ON_3dPoint& );


    bool CalculateTransform( CRhinoViewport&, const ON_3dPoint&, ON_Xform& );


  private:
    const CRhinoInstanceDefinition* m_idef;
    ON_Xform m_xform;
    bool m_bDraw;
  };


  CGetBlockInsertPoint::CGetBlockInsertPoint( const CRhinoInstanceDefinition* idef )
  : m_idef(idef)
  {
    m_xform.Identity();
    m_bDraw = false;
  }


  void CGetBlockInsertPoint::OnMouseMove( 
      CRhinoViewport& vp, 
      UINT flags, 
      const ON_3dPoint& pt, 
      const CPoint* p 
      )
  {
    m_bDraw = CalculateTransform( vp, pt, m_xform );
    CRhinoGetPoint::OnMouseMove( vp, flags, pt, p );
  }


  void CGetBlockInsertPoint::DynamicDraw( 
      HDC hdc, 
      CRhinoViewport& vp, 
      const ON_3dPoint& pt 
      )
  {
    if( m_idef && m_bDraw )
    {
      CRhinoDisplayPipeline* dp = vp.DisplayPipeline();
      if( dp )
      {
        dp->PushObjectColor( 0 );
        dp->DrawObject( m_idef, &m_xform );
        dp->PopObjectColor();
      }
    }
    CRhinoGetPoint::DynamicDraw( hdc, vp, pt );
  }


  bool CGetBlockInsertPoint::CalculateTransform( 
      CRhinoViewport& vp, 
      const ON_3dPoint& pt, 
      ON_Xform& xform 
      )
  {
    bool rc = false;
    ON_3dVector v = pt - BasePoint();
    if( v.IsTiny() )
      xform.Identity();
    else
      xform.Translation( v );
    return xform.IsValid();
  }

Example

The following example code demonstrates how to insert a block definition into the Rhino document and allow the user to interactively pick the insertion point.

  CRhinoCommand::result CCommandTest::RunCommand( const CRhinoCommandContext& context )
  {
    // Prompt for instance definition to insert
    CRhinoGetString gs;
    gs.SetCommandPrompt( L"Name of block to insert" );
    gs.GetString();
    if( gs.CommandResult() != success )
      return gs.CommandResult();


    ON_wString idef_name = gs.String();
    idef_name.TrimLeftAndRight();
    if( idef_name.IsEmpty() )
      return nothing;


    // Find specified instance definition
    CRhinoInstanceDefinitionTable& idef_table = context.m_doc.m_instance_definition_table;
    int idef_index = idef_table.FindInstanceDefinition( idef_name );
    if( idef_index < 0 )
    {
      RhinoApp().Print( L"Unable to insert \"%s\". Block not found.\n", idef_name );
      return nothing;
    }


    // Get instance definition
    const CRhinoInstanceDefinition* idef = idef_table[idef_index];
    if( !idef || idef->IsDeleted() )
      return nothing;


    // Pick an insert point
    CGetBlockInsertPoint gp( idef );
    gp.SetCommandPrompt( L"Insertion point" );
    gp.SetBasePoint( ON_origin );
    gp.GetPoint();
    if( gp.CommandResult() != success )
      return gp.CommandResult();


    // Get active view
    CRhinoView* view = gp.View();
    if( !view )
    {
      view = RhinoApp().ActiveView();
      if( !view )
        return failure;
    }


    // Calculate final xform
    ON_Xform xform;
    if( gp.CalculateTransform(view->ActiveViewport(), gp.Point(), xform) )
    {
      idef_table.AddInstanceObject( idef_index, xform );
      context.m_doc.Redraw();
    }


    return success;
  }