The area of an intersection of two AcDbRegion

By Xiaodong Liang

The following sample demonstrates the function AcDbRegion::booleanOper() to perform intersection on two acdbRegion entities. If the entities selected are not regions, then they are converted to regions using
AcDbRegion::createFromCurves(). Since region intersection is handled by ACIS, it will be quite slow for a large number of regions.

static void regionBoolean()     {          // TODO: Implement the command          ads_name e1;          ads_name e2;          ads_point p1;          if (RTNORM != acedEntSel(L"nSelect First                                      region",e1,p1))          {           acutPrintf(L"nFailed to select first entity");           return;          }          if (RTNORM != acedEntSel(L"nSelect Second                                      region",e2,p1))          {           acutPrintf(L"nFailed to select second entity");           return;          }               AcDbObjectId objId1 = NULL;                  AcDbObjectId objId2 = NULL;           Acad::ErrorStatus es;          es = acdbGetObjectId (objId1 , e1);          if (Acad::eOk != es)          {           acutPrintf(L"nFailed to get object Id of first                           entity");           return;          }               es = acdbGetObjectId (objId2 , e2);          if (Acad::eOk != es)          {           acutPrintf(L"nFailed to get object Id of second                              entity");           return;          }          //If entities selected are not regions           // then convert them to regions          AcDbRegion* pReg1=NULL;          AcDbRegion* pReg2=NULL;;               es = acdbOpenObject (pReg1,                                objId1,                     &#1
60;          AcDb::kForWrite,                                Adesk::kFalse);          if(Acad::eOk != es)          {           acutPrintf(L"nFirst entity selected is not a region,                   it will be converted to a region internally");          }               es = acdbOpenObject                  (pReg2,objId2,AcDb::kForWrite,Adesk::kFalse);          if(Acad::eOk != es)          {           acutPrintf(L"nSecond entity selected is not a            region, it will be converted to a region internally");          }          AcDbVoidPtrArray curves;          AcDbVoidPtrArray regions;          AcDbEntity *pEnt1 = NULL;          AcDbEntity *pEnt2 = NULL;          if (pReg1 == NULL) //Not a region entity          {           es =acdbOpenAcDbEntity(pEnt1,objId1,            AcDb::kForRead,Adesk::kFalse);           if(Acad::eOk != es)           {            acutPrintf(L"nFailed to open first entity for                              write");            return;           }           curves.append(pEnt1);               pEnt1->close();          }          if (pReg2 == NULL) //Not a region entity          {               es =acdbOpenAcDbEntity(pEnt2,objId2,                AcDb::kForRead,Adesk::kFalse);               if(Acad::eOk != es)               {                acutPrintf(L"nFailed to open second entity for                            write");                return;               }               curves.append(pEnt2);                   pEnt2->close();          }          if (pReg1 ==  NULL || pReg2 ==    NULL)           es=AcDbRegion::createFromCurves(curves,regions);          if (pReg1 ==  NULL)           pReg1 = AcDbRegion::cast((AcRxObject*)regions[0]);          if (pReg2 ==  NULL && regions.length() > 1)           pReg2 = AcDbRegion::cast((AcRxObject*)regions[1]);          if (pReg2 ==  NULL && regions.length() == 1)           pReg2 = AcDbRegion::cast((AcRxObject*)regions[0]);               // after boolean operation region 2 is deleted           // and region 1 is updated          // with resultant region.          es = pReg1->booleanOper( AcDb::kBoolIntersect, pReg2);          if(Acad::eOk == es)          {           double rarea;           es = pReg1->getArea(rarea);           if(Acad::eOk != es)           {            acutPrintf(L"nFailed to get area");               }               else           {            acutPrintf(L"nArea of intersected region is = %lf",             rarea);           }              }          else          {           acutPrintf(L"nFailed to intersect regions");          }          pReg1->close();          pReg2->close();     }