Summary: Demonstrates how to move curve and surface object grips.

How to move the control points of a curve or surface object using the Rhino SDK?

The curve and surface grips you see on the screen, after running Rhino's PointsOn command, are represented by CRhinoGripObject-derived objects. To move a grip object, you have to do a few things:

1. Get a CRhinoGripObject. You can use a CRhinoGetObject object to do this.
2. Call CRhinoGripObject::MoveGrip to transform the grip's location.
3. Call CRhinoGripObject::Owner to get the grips owning CRhinoObject object.
4. Call CRhinoObject::NewObject to create a new CRhinoObject object based on the new grip location.
5. Call CRhinoDoc::ReplaceObject to replace the original owning object with the new one.

The following sample code demonstrates this. Note, this sample uses a CRhinoXformObjectList object to make maintain the list of grips and grip owners easier.

 
CRhinoCommand::result CCommandMoveGrips::RunCommand( const CRhinoCommandContext& context )
{
  CRhinoGetObject go;
  go.SetCommandPrompt( L"Select grips to move" );
  go.SetGeometryFilter( CRhinoGetObject::grip_object );
  go.GetObjects( 1, 0 );
  if( go.CommandResult() != success )
    return go.CommandResult();
 
  CRhinoXformObjectList xform_list;
  if( xform_list.AddObjects(go, true) < 1 )
    return failure;
 
  CRhinoGetPoint gp;
  gp.SetCommandPrompt( L"Point to move from" );
  gp.GetPoint();
  if( gp.CommandResult() != success )
    return gp.CommandResult();
 
  ON_3dPoint from = gp.Point();
 
  gp.SetCommandPrompt( L"Point to move to" );
  gp.SetBasePoint( from );
  gp.DrawLineFromPoint( from, TRUE );
  gp.GetPoint();
  if( gp.CommandResult() != success )
    return gp.CommandResult();
 
  ON_3dPoint to = gp.Point();
 
  ON_Xform xform;
  xform.Translation( to - from );
  if( xform.IsValid() )
  {
    // Transform the grip objects
    int i;
    for( i = 0; i < xform_list.m_grips.Count(); i++ )
      xform_list.m_grips[i]->MoveGrip( xform );
 
    // Replace the old owner with a new one
    for( i = 0; i < xform_list.m_grip_owners.Count(); i++ )
    {
      CRhinoObject* old_object = xform_list.m_grip_owners[i];
      if( old_object )
      {
        CRhinoObject* new_object = old_object->m_grips->NewObject();
        if( new_object )
          context.m_doc.ReplaceObject( CRhinoObjRef(old_object), new_object, true );
      }
    }
 
    context.m_doc.Redraw();
  }
 
  return success;
}

 
Public Overrides Function RunCommand(ByVal context As RMA.Rhino.IRhinoCommandContext) As RMA.Rhino.IRhinoCommand.result
 
  Dim go As New MRhinoGetObject
  go.SetCommandPrompt("Select grips to move")
  go.SetGeometryFilter(IRhinoGetObject.GEOMETRY_TYPE_FILTER.grip_object)
  go.GetObjects(1, 0)
  If (go.CommandResult() <> IRhinoCommand.result.success) Then
    Return go.CommandResult()
  End If
 
  Dim list As New MRhinoXformObjectList
  If (list.AddObjects(go, True) < 1) Then
    Return IRhinoCommand.result.failure
  End If
 
  Dim gp As New MRhinoGetPoint
  gp.SetCommandPrompt("Point to move from")
  gp.GetPoint()
  If (gp.CommandResult() <> IRhinoCommand.result.success) Then
    Return gp.CommandResult()
  End If
 
  Dim pt_start As On3dPoint = gp.Point()
 
  gp.SetCommandPrompt("Point to move to")
  gp.SetBasePoint(pt_start)
  gp.DrawLineFromPoint(pt_start, True)
  gp.GetPoint()
  If (gp.CommandResult() <> IRhinoCommand.result.success) Then
    Return gp.CommandResult()
  End If
 
  Dim pt_end As On3dPoint = gp.Point()
 
  Dim xform As New OnXform
  xform.Translation(pt_end - pt_start)
  If xform.IsValid() Then
    Dim i As Integer = 0
    For i = 0 To list.m_grips.Length - 1
      list.m_grips(i).MoveGrip(xform)
    Next
    For i = 0 To list.m_grip_owners.Length - 1
      Dim old_object As MRhinoObject = list.m_grip_owners(i)
      Dim new_Object As MRhinoObject = old_object.m_grips.NewObject()
      If (new_Object IsNot Nothing) Then
        context.m_doc.ReplaceObject(New MRhinoObjRef(old_object), new_Object, True)
      End If
    Next
    context.m_doc.Redraw()
  End If
 
  Return IRhinoCommand.result.success
 
End Function