APXMRK-bgol (Mark Apex Points Along an Alignment)

Command Type: AutoLISP routine (works in AutoCAD, BricsCAD, ZWCAD and most AutoLISP-compatible CAD platforms)
Developed by: BGol Community, bgol.in

Inspired by the general concept of apex/PI marking utilities used in alignment design documentation. This is an original, independently written routine, new file name, new command name, new source code, created so the CAD community has a free, editable, open-source alternative.

Overview

APX marks every internal vertex (apex, or Point of Intersection) of one or more selected alignment polylines with a triangle marker, while marking the polyline's start and end points with a distinct square marker, making the alignment's structure immediately clear at a glance.

How to Use

1. Load APXMRK-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type APX at the command line and press Enter.
3. Select one or more alignment polylines (multiple polylines can be processed in a single run).
4. Press Enter to finish selection.
5. Every internal vertex is marked with a red triangle on layer BGOL-APX; the first and last vertex of each polyline is marked with a green square on layer BGOL-APX-END.
6. A summary of apex points and start/end points marked is echoed to the command line.

Why Use It

• Automates standard documentation, marks every PI/apex point across an entire polyline (or multiple polylines) in one command, instead of manually placing markers vertex by vertex.
• Clear structure at a glance, distinguishing start/end points from internal apex points communicates the alignment's shape instantly to reviewers.
• Batch operation, processes multiple selected polylines together, saving time on drawings with several alignments or branch alignments.

Where to Use It

• Documenting horizontal alignment geometry for road, rail, or channel design, where apex/PI points need clear marking for design review or construction reference.
• Preparing alignment drawings ahead of curve-design work, where apex points define where curves need to be introduced.
• Any infrastructure drafting task needing quick visual identification of an alignment's direction-change points.

Notes

• Marker size defaults to 1.2 drawing units; edit the size argument in the BGOL:APX-DrawTriangle / BGOL:APX-DrawSquare calls in C:APX to change it.
• Works on LWPOLYLINE entities; vertices are read via the polyline's Coordinates property.
• Source code is fully open, feel free to study, modify, and redistribute it under the same open, free-for-all spirit.

Credits

Developed and shared for the CAD community by BGol Community. Website: https://bgol.in/ Free and open-source, use it, modify it, share it, for personal or commercial work alike.