Pick any line, arc, open polyline, spline or elliptical arc, and FOLLOWON selects everything joined to it end to end — then everything joined to those, and so on outwards until the chain runs out.
What FollowOn does
This is the tool for grabbing a complete pipe run, a kerb line, a services route or a site boundary that was drawn as forty separate segments by someone who had never heard of PEDIT.
One pick replaces a fence selection, or a great deal of shift-clicking along something that curves.
How to use it
- Load the routine with
APPLOAD, or put it on your support file search path. - Type
FOLLOWON. - Pick any one object in the chain.
- The whole connected run is selected, ready for the next command.
How it works
The search works outwards in waves. It starts with the endpoints of the picked object, then repeatedly sweeps the remaining candidates looking for any whose start or end point coincides with a point already in the chain. Every match found is added, its endpoints join the frontier, and the sweep runs again. When a full sweep adds nothing new, the chain is complete.
Objects already matched are removed from the candidate pool each round, so the search gets faster as it goes rather than repeatedly re-testing the same geometry. On a long run that is the difference between usable and not.
Closed objects are excluded by design. A closed polyline, a circle or a full ellipse has no free ends, so it can neither continue a chain nor be continued from. Including them would mean a chain that merely touched a circle would stop dead there. The selection filter rejects them outright.
Notes and limits
- Endpoints must actually coincide. Segments that only look joined, or that overlap without sharing an endpoint, break the chain — which is often exactly what you want to discover.
- Closed objects cannot be picked or included. Circles and closed polylines have no ends.
- A branch stops nothing. If three segments meet at a point, all of them are picked up — the chain grows in every direction it can.
- It only selects, so nothing is changed and there is no undo group.
Download and details
| Name | FollowOn — select a whole connected chain of curves from one pick |
| Download | FollowOn.lsp — 10.6 KB, plain AutoLISP source. Downloads directly; no zip to unpack. |
| Type | AutoCAD AutoLISP routine |
| Command | FOLLOWON |
| Requires | the ActiveX layer (loaded automatically by the routine with vl-load-com). |
| Source size | 10.6 KB, 259 lines |
| Error handling | Yes — a *error* handler restores every system variable it changed, on cancel as well as on error. |
| Undo | Not needed — this routine only reads the drawing and changes nothing. |
| Compatibility | AutoCAD (any release with AutoLISP), BricsCAD, ZWCAD, GstarCAD, ProgeCAD and other IntelliCAD-based platforms. AutoCAD LT needs a LISP enabler. No .NET, no ObjectARX, no installer. |
| Author | YZ, August 2026 |
| Licence | Free to use, supplied “as is” with no warranty. |
References
- TAPE LISP — total the length of the chain once you have it selected
- CORRAL LISP — select everything inside a boundary instead of along a chain
- CURVEHUG LISP — place symbols along the run you have found
- More free AutoLISP routines on this site
- Wisey’s Steel Shapes — free structural steel section drawing program