вопрос по getOsnapPoints

Изучаю как работает сабж для entity. вот код:
AcDbObjectId  createLine()
{
    AcGePoint3d startPt(4.0, 2.0, 0.0);
    AcGePoint3d endPt(100.0, 100.0, 0.0);
    AcDbLine *pLine = new AcDbLine(startPt, endPt);
    AcDbBlockTable *pBlockTable;
    acdbHostApplicationServices()->workingDatabase()
        ->getSymbolTable(pBlockTable, AcDb::kForRead);
    AcDbBlockTableRecord *pBlockTableRecord;
    pBlockTable->getAt(ACDB_MODEL_SPACE, pBlockTableRecord,
        AcDb::kForWrite);
    pBlockTable->close();
    AcDbObjectId lineId;
    pBlockTableRecord->appendAcDbEntity(lineId, pLine);
    pBlockTableRecord->close();
    pLine->close();
    return lineId ;
}
void osnapline()
{
    AcGePoint3d lastPoint,pickPoint,Pt(90.0, 10.0, 0.0);
    AcGeMatrix3d mat;mat.setToIdentity();
    AcGePoint3dArray pSnaps;
    AcDbEntity* pEnt = NULL;
    AcDbIntArray gomIDs;
    pickPoint = Pt;
    lastPoint = pickPoint;
    AcDbObjectId id = createLine();
    acdbOpenAcDbEntity(pEnt,id,AcDb::kForRead);
    pEnt->getOsnapPoints(AcDb::kOsModeEnd,0,pickPoint,lastPoint,mat,pSnaps,gomIDs);
    for (int i=0; i< pSnaps.length(); i++) {
          acutPrintf(_T("\np[%d]=(%g,%g,%g)"),i+1,pSnaps[i][X],pSnaps[i][Y],pSnaps[i][Z]);
        }
    pEnt->close();
}
The pickPoint argument provides the point (in WCS coordinates) that started this osnap operation. Вот это не совсем понимаю. Какой смысл у pickPoint?