ANGMRK-bgol (Mark Interior & Exterior Angles)

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 vertex-angle marking utilities used in civil/survey drafting. 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

AGMK calculates and marks both the interior and exterior angle at every internal vertex of a selected polyline. Each vertex gets a small circular marker plus a text label showing both angle values (which always sum to 360 degrees), making it fast to review sharp corners, verify boundary geometry, or check curve/intersection design.

How to Use

1. Load ANGMRK-bgol.lsp into your CAD session (drag-and-drop the file onto the drawing window, or use the APPLOAD command).
2. Type AGMK at the command line and press Enter.
3. Select the polyline you want to analyze.
4. Every internal vertex (all vertices except the first and last on an open polyline) is marked with a small circle and a text label showing interior° / exterior°, placed on a dedicated layer, BGOL-AGMK (colour cyan).

Why Use It

• Saves time, automates angle marking, eliminating manual protractor-style measurement or trigonometric calculation at every vertex.
• Improves accuracy, removes human error from angle determination.
• Enhances efficiency, frees the designer to focus on higher-level design decisions rather than tedious angle bookkeeping.

Where to Use It

• Site planning and layout, analyzing drainage patterns, property lines, and efficient site layouts.
• Structural analysis, understanding angles between connected structural elements such as retaining walls or support beams.
• Road and pathway design, designing curves, intersections, and slopes that depend on angles between alignment segments.
• QA review of boundary or alignment geometry where sharp or unusual angles need to be flagged.

Notes

• Only internal vertices are marked; the first and last vertex of an open polyline have no "interior" angle and are skipped.
• Interior and exterior angle values always sum to 360 degrees at each vertex, matching the convention used by comparable angle-marking tools.
• 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.