Getting the Midpoint of each Polyline Segment using ObjectARX

By Fenton Webb

An AcDbPolyline is derived from AcDbCurve, a curve uses Parameter values to define its geometry. For a Polyline, the Parameter start value is 0 and the end parameter is the total number of vertices –1. Those parameter values can be utilized to quickly and easily work out mid points, like this:

Acad::ErrorStatus getMidPointOnEachSegOfCrv(AcDbCurve *pCurve)        {          if(!pCurve->isKindOf(AcDbCurve::desc()))          {            acutPrintf(L"nSelected entity is not a CURVE derived object");            return Acad::eInvalidInput;          }                   Acad::ErrorStatus es;          double startParam, endParam;          // get the start param, usually it starts at 0 or 1          es = pCurve->getStartParam( startParam );          acutPrintf(L"nstartParam is %fl", startParam);                   // get the end param, for a polyline it's the total number of          // vertex's -1          es =  pCurve->getEndParam( endParam );          acutPrintf(L"nendParam is %fl", endParam);          // now loop the parameters, adding 1.0 each iteration          for(double i=startParam; igetPointAtParam(i+.5, pt);            if (es == Acad::eOk)              acutPrintf(L"n%f,%f,%f", pt[0], pt[1], pt[2]);          }                   return Acad::eOk;        }