Deleting a Vertex from an AcDbPolyline3d using ObjectARX

by Fenton Webb

Removing a vertex from an AcDbPolyline3d is a little more tricky than you would think. An AcDbPolyline3d is what’s known as a ‘Complex’ entity type, it’s vertex data are contained inside of external AcDbVertex3d entities. So to delete a vertex, you have to find the vertex entity and then delete it using the erase() method.

Here’s what I mean…

#include     void deleteVertex()     {          ads_name polyName;           ads_point pt;          if(acedEntSel(_T("nSelect a 3d polyline: "), polyName, pt) != RTNORM)                 return;                AcDbObjectId    polyId;           acdbGetObjectId(polyId, polyName);           // get the polyline in an autoptr      AcDbObjectPointer pPoly(polyId, AcDb::kForRead);      Acad::ErrorStatus es = pPoly.openStatus();      // if it didn't open      if(es != Acad::eOk)       {         if (es == Acad::eNotThatKindOfClass)          acutPrintf(_T("nYou did not select a 3d polyline."));                 else          acutPrintf(_T("nError opening entity."));                return;          }               // add each vertex to objectId array          AcDbObjectIdArray vertexArray;          AcDbObjectIterator *pIter = pPoly->vertexIterator();          for(pIter->start(); !pIter->done(); pIter->step())                 vertexArray.append(pIter->objectId());          delete pIter;           // get vertex to delete          ACHAR prompt[256];          acutPrintf(prompt,_T( "nSelect vertex to delete (1-%d): "),                                         vertexArray.length());          int delVertex = -1;          if(acedGetInt(prompt, &delVertex) != RTNORM)               return;          if(delVertex < 1 || delVertex > vertexArray.length())      {                acutPrintf(_T("nInvalid vertex number."));                return;          }              // open the vertex entity and delete it          AcDbObjectPointer pObj(vertexArray[delVertex-1],                                                 AcDb::kForWrite);      if(pObj.openStatus() != Acad::eOk)       {               acutPrintf(_T("nError opening vertex: %d"), delVertex);                return;          }         pObj->erase();        }         NOTE: If you are using .NET, you have to follow the same logic.