Question

I understand that, using a MRhinoGetObject object, I can select a group of objects. But, how can I select a group of objects non-interactively, or without the user having to pick one of the group members?

Answer

To non-interactively select all of the objects that belong to an object group, you must iterate through the geometry table and look for all of the group members.

For example:

C#

  public int SelectObjectGroup(MRhinoDoc doc, int group_index, bool bRedraw)
  {
    if( group_index < 0 || group_index >= doc.m_group_table.GroupCount() )
      return 0;


    MRhinoObjectIterator it = new MRhinoObjectIterator(doc,IRhinoObjectIterator.object_state.undeleted_objects,
                                                           IRhinoObjectIterator.object_category.active_and_reference_objects );
    it.IncludeLights(true);
    it.IncludePhantoms(true);


    int selected_count = 0;
    foreach (MRhinoObject obj in it)
    {
      if (obj.Attributes().IsInGroup(group_index) && obj.IsSelectable() )
      {
        obj.Select();
        selected_count++;
      }
    }


    if (bRedraw)
      doc.Redraw();


    return selected_count;
  }

Here is an example, perhaps not a good one, of using the above function.

  public override IRhinoCommand.result RunCommand(IRhinoCommandContext context)
  {
    MRhinoGetObject go = new MRhinoGetObject();
    go.SetCommandPrompt("Select object");
    go.GetObjects(1, 1);
    if (go.CommandResult() != IRhinoCommand.result.success)
      return go.CommandResult();


    IRhinoObject obj = go.Object(0).Object();
    if( obj == null)
      return IRhinoCommand.result.failure;


    int group_count = obj.Attributes().GroupCount();
    if( group_count > 0 )
    {
      Arrayint groups  = new Arrayint(group_count);
      obj.Attributes().GetGroupList(ref groups);


      for (int i = 0; i < groups.Count(); i++)
        SelectObjectGroup(context.m_doc, groups[i], false);


      context.m_doc.Redraw();
    }


    return IRhinoCommand.result.success;
  }