Function Syntax: ExtendStartEndMultiple Version: 1.0 Date: 20.06.2026 6:38:59PM AI+ https://www.lee-mac.com/doubleextend.html Description 🧩 ExtendStartEndMultiple extends the start and end of multiple selected LINE ARC LWPOLYLINE and POLYLINE objects using independent extension values. 🎛️ The DCL interface provides separate Start and End values together with Apply Undo OK and Cancel. ↩️ Apply can be tested repeatedly and Undo reverses the most recent Apply while Cancel restores the geometry changed during the current run. Function Syntax Main command: ExtendStartEndMultiple SEO Optimized Overview 📐 The routine is based on Lee Mac DoubleExtend logic and supports straight and curved polyline geometry. 🖱️ Source entities are selected before the DCL loop starts. ➡️ Extend Start and Extend End are independent values so each end can be lengthened by a different amount. 🧬 Lightweight polyline vertex and bulge calculations preserve supported curved end geometry. ✅ OK performs one apply when no Apply or Undo interaction has yet occurred and otherwise accepts the current state. ↩️ Cancel reverses all Apply operations created during the current command session. 🧱 The complete command is wrapped in an outer AutoCAD UNDO group. Primary Workflow • Run ExtendStartEndMultiple. • Select LINE ARC LWPOLYLINE or POLYLINE objects. • Enter independent Extend Start and Extend End values. • Use Apply to modify the selected geometry while keeping the dialog workflow active. • Use Undo to reverse the latest Apply. • Use OK to keep the current result or Cancel to restore the changes made during this run. Functionalities ✅ Multiple object processing - extends a selection of supported curve entities. ✅ Independent start extension - uses a separate value for the beginning of each curve. ✅ Independent end extension - uses a separate value for the end of each curve. ✅ LINE support - extends straight lines. ✅ ARC support - extends supported arc geometry. ✅ LWPOLYLINE support - extends lightweight polyline endpoints. ✅ Legacy POLYLINE support - processes supported old polyline geometry. ✅ Apply workflow - allows iterative changes without leaving the tool. ✅ Undo last Apply - reverses the latest Apply operation. ✅ Cancel rollback - restores Apply changes from the current session. ✅ Undo grouping - groups the command modifications for AutoCAD undo. Important Commands and Aspects 🧩 LM:dex:extendpoly calculates extended lightweight polyline endpoint geometry. 🧩 LM:dex:run applies the extension logic to the current selection. 🧩 DEX:dialog returns OK Apply Undo or Cancel state to the main loop. Result 🎯 The result is the original selected curve geometry lengthened independently at its start and end. 🔄 The command supports iterative adjustment before the user accepts the final state. Important Notes ⚠️ The file is based on original DoubleExtend logic by Lee Mac. ⚠️ Cancel is designed to reverse Apply operations from the current command run. ⚠️ The current selection filter accepts LINE ARC LWPOLYLINE and POLYLINE. SEO Keywords 🏷️ AutoCAD, 🏷️ Civil 3D, 🏷️ AutoLISP, 🏷️ ExtendStartEndMultiple, 🏷️ DoubleExtend, 🏷️ Lengthen, 🏷️ Polyline extension, 🏷️ Start extension, 🏷️ End extension, 🏷️ Apply, 🏷️ Undo, 🏷️ DCL