线段等分/定长的实现

线段等分/定长实现方法

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#线段等分/定长的实现

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本文介绍了如何在CAD环境中，通过GetPointAtDist方法实现在线段（如PLine、line、arc）上按给定长度获取等分点。该方法是Curve基类的一部分，适用于不同的曲线类型，并且强调线段总长的方法在子类中存在，例如arc.Length、line.Length和polyline.Length。示例展示了如何应用这些方法进行线段的等分标志点设置。

//方法名称:GetPointAtDist
//拥有者:Curve（基类）及line arc polyline…
//返回值:point3d
//功能描述:返回曲线上距起点某距离值处的点。
//类似方法：GetParameterAtDistance
//相关备注：线段总长方法仅仅在子类中才有，基类没有
比如：arc.Length line.Length polyline.Length

范例：在CAD中对PLine（line arc 同样适用）线段按给定长度进行标志点(等分)

private void My_div() // 求等分点或定长点
            {
 Autodesk.AutoCAD.ApplicationServices.Document acDoc = Autodesk.AutoCAD.ApplicationServices.Application.DocumentManager.MdiActiveDocument;
                Editor ed = acDoc.Editor;
                Database acCurDb = acDoc.Database;
                Entity acEnt = null;
                Curve curve = null;
                Polyline polyline = null;
                PromptEntityResult result = ed.GetEntity("选择多义线");
                if (result.Status == PromptStatus.OK)
                {
                    using (Autodesk.AutoCAD.DatabaseServices.Transaction acTrans = acCurDb.TransactionManager.StartTransaction())
                    {
                        BlockTable acBlkTbl;
                        acBlkTbl = acTrans.GetObject(acCurDb.BlockTableId, OpenMode.ForRead) as BlockTable;
                        //以写模式打开 Block 表记录 Model 空间
                        BlockTableRecord acBlkTblRec;
                        acBlkTblRec = acTrans.GetObject(acBlkTbl[BlockTableRecord.ModelSpace], OpenMode.ForWrite) as BlockTableRecord;
    
                        acEnt = acTrans.GetObject(result.ObjectId, OpenMode.ForWrite) as Entity;
                        curve = acTrans.GetObject(acEnt.ObjectId, OpenMode.ForWrite) as Curve;//curve是line arc polyline。。。的父类
                       polyline = acTrans.GetObject(acEnt.ObjectId, OpenMode.ForWrite) as Polyline;
                        Double Dist = 103;
                        MessageBox.Show("\n 多段线长度:" + polyline.Length);
                         int n;
                        //点位
                        for (n = 1; (int)(polyline.Length / Dist) >= n; n++)
                        {
                            using (DBPoint pt = new DBPoint(new Point3d(curve.GetPointAtDist(Dist * n).X, curve.GetPointAtDist(Dist * n).Y, curve.GetPointAtDist(Dist * n).Z)))
                            {
                                 acBlkTblRec.AppendEntity(pt);
                                acTrans.AddNewlyCreatedDBObject(pt, true);
                              }
                        }
                      acTrans.Commit();
                    }
                }
                //更改点样式
                acCurDb.Pdmode = 35;
                acCurDb.Pdsize = 0.5;
            }